On May 3, 2021, we entered into sales agreements with each of J.P. Morgan Securities LLC, Barclays Capital Inc., BMO Capital Markets Corp., Credit Agricole Securities (USA) Inc., Deutsche Bank Securities Inc., Fifth Third Securities, Inc., Goldman Sachs & Co. LLC, Jefferies LLC, KeyBanc Capital Markets Inc., Morgan Stanley & Co. LLC, MUFG Securities Americas Inc., RBC Capital Markets, LLC, Stifel, Nicolaus & Company, Incorporated, TD Securities (USA) LLC and Truist Securities, Inc. (each, a "Sales Agent" and collectively, the "Sales Agents") and, as applicable, the relevant Forward Purchasers (as defined below), relating to the offering of shares of our common stock, par value $0.01 per share, having an aggregate gross sales price of up to $750,000,000, to be made from time to time under this prospectus supplement and the accompanying prospectus through the Sales Agents, acting as our sales agents or, if applicable, as Forward Sellers (as defined below), or directly to the Sales Agents as principals for their own accounts.

In accordance with the terms of the sales agreements, sales, if any, of shares of our common stock under this prospectus supplement and the accompanying prospectus made through the Sales Agents, as our sales agents, or as Forward Sellers pursuant to the sales agreements, may be made (1) in "at the market" offerings (as defined in Rule 415 under the Securities Act of 1933, as amended (the "Securities Act")) by means of ordinary brokers' transactions at market prices prevailing at the time of sale, including sales made on the NASDAQ Global Select Market, sales made to or through market makers and sales made through other securities exchanges or electronic communications networks and (2) in such privately negotiated transactions, which may include block trades, as we and any Sales Agent or Forward Seller may agree.

Under the terms of the sales agreements, we also may sell shares of our common stock to any Sales Agent as principal for its own account. If we sell shares to any Sales Agent as principal, we will enter into a separate terms agreement setting forth the terms of such transaction, and we will describe the agreement in a separate prospectus supplement or pricing supplement. In any such sale to a Sales Agent as principal, we may agree to pay the applicable Sales Agent a commission or underwriting discount that may exceed 2.0% of the gross sales price per share of common stock sold to such Sales Agent, as principal.

No Sales Agent, whether acting as our sales agent or as Forward Seller, is required to sell any specific number or dollar amount of shares of our common stock but, subject to the terms and conditions of the sales agreements, each Sales Agent has agreed to use its commercially reasonable efforts, consistent with its normal trading and sales practices and applicable law and regulations, to sell all of the shares of our common stock so designated by us (if acting as our sales agent) and all of the shares borrowed by the relevant Forward Purchaser pursuant to the relevant sales agreement (if acting as Forward Seller), in each case, on the terms and subject to the conditions of the relevant sales agreement. There is no arrangement for shares to be received in an escrow, trust or similar arrangement. The offering of shares of our common stock pursuant to the sales agreements will terminate upon the earlier of (i) the sale of shares of our common stock subject to the sales agreements (including shares sold by us to or through the Sales Agents and borrowed shares sold through the Sales Agents, acting as Forward Sellers) and any terms agreement having an aggregate gross sales price of $750,000,000 and (ii) with respect to a particular sales agreement or terms agreement, the termination of such sales agreement by us or by the applicable Sales Agent as permitted therein.

The sales agreements contemplate that, in addition to the issuance and sale by us of shares of our common stock to or through the Sales Agents as our sales agents, we may enter into separate forward sale agreements (each, together with any related pricing supplement a "forward sale agreement" and, collectively, the "forward sale agreements"), with any of JPMorgan Chase Bank, National Association, Barclays Bank PLC, Bank of Montreal, Crédit Agricole Corporate and Investment Bank, Deutsche Bank AG, London Branch, Goldman Sachs & Co. LLC, Jefferies LLC, KeyBanc Capital Markets Inc., Morgan Stanley & Co. LLC, MUFG Securities EMEA plc, Royal Bank of Canada, The Toronto-Dominion Bank and Truist Bank or one of their respective affiliates (in such capacity, each, a "Forward Purchaser" and, collectively, the "Forward Purchasers"). If we enter into a forward sale agreement with any Forward Purchaser, we expect that such Forward Purchaser, acting in accordance with the mutually accepted instructions related to such forward sale agreement, will attempt to borrow and sell, through the relevant Sales Agent, acting as sales agent for such Forward Purchaser, shares of our common stock to hedge such Forward Purchaser's exposure under such forward sale agreement. We refer to a Sales Agent, when acting as sales agent for the relevant Forward Purchaser, as, individually, a "Forward Seller" and, collectively, the "Forward Sellers". Each Forward Purchaser will be either one of the Sales Agents named in the first sentence of this paragraph or an affiliate of one of those Sales Agents and, unless otherwise expressly stated or the context otherwise requires, references herein to the "related" or "relevant" Forward Purchaser mean, with respect to any Sales Agent, the affiliate of such Sales Agent that is acting as Forward Purchaser or, if applicable, such Sales Agent acting in its capacity as Forward Purchaser. We will not initially receive any proceeds from any sale of shares of our common stock borrowed by a Forward Purchaser and sold through a Forward Seller.

We expect to fully physically settle each forward sale agreement, if any, with the relevant Forward Purchaser on one or more dates specified by us on or prior to the maturity date of such forward sale agreement. If we elect to cash settle any forward sale agreement, we may not receive any proceeds and we may owe cash to the relevant Forward Purchaser. If we elect to net share settle any forward sale agreement, we will not receive any proceeds, and we may owe shares of our common stock to the relevant Forward Purchaser. See "Plan of Distribution—Sales Through Forward Sellers".

The compensation to each Sales Agent will be a mutually agreed commission that will not exceed, but may be lower than, 2.0% of the gross sales price of the shares sold through it as our sales agent pursuant to the applicable sales agreement. The compensation to each Sales Agent acting as a Forward Seller will be a mutually agreed commission in the form of a reduction to the initial forward price under the related forward sale agreement that will not exceed, but may be lower than, 2.0% of the gross sales price of the borrowed shares sold through such Sales Agent, acting as Forward Seller, during the applicable forward hedge selling period for such shares (which gross sales price will be adjusted for daily accruals based on a floating interest rate and specified amounts related to expected dividends on shares of our common stock if an "ex-dividend" date occurs during such forward hedge selling period). We refer you to "Plan of Distribution" beginning on page S-12 of this prospectus supplement for additional information regarding compensation of the Sales Agents.

We intend to contribute the net proceeds from any sales of shares of our common stock to or through the Sales Agents and the net proceeds, if any, from the settlement of any forward sale agreements to our operating partnership in exchange for an equivalent number of newly issued operating partnership units in accordance with the partnership agreement of our operating partnership. Our operating partnership intends to use the proceeds contributed by us for general corporate purposes, which may include funding future acquisitions, investments or capital expenditures and repaying outstanding indebtedness, including borrowings under our senior unsecured revolving credit facility.

To assist us in complying with certain U.S. federal income tax requirements applicable to real estate investment trusts ("REITs"), among other purposes, our charter contains certain restrictions relating to the ownership and transfer of our stock, including an ownership limit of 9.8% of our outstanding common stock, subject to certain exceptions. See "Restrictions on Ownership and Transfer" in the accompanying prospectus for a detailed description of the ownership and transfer restrictions applicable to our common stock.

Pursuant to separate sales agreements, each dated as of May 6, 2020, we previously offered and sold shares of our common stock having an aggregate offering price of approximately $599.2 million by means of a prospectus supplement dated May 6, 2020 and the accompanying prospectus dated May 3, 2019 and pursuant to a Registration Statement on Form S-3 (Registration No. 333-231203) filed on May 3, 2019 (the "Prior Offering"). The Prior Offering has been terminated, with shares of our common stock having an aggregate offering price of approximately $150.8 million remaining unsold.

Our common stock is listed on the NASDAQ Global Select Market under the symbol "CONE". On May 3, 2021, the last reported sale price of our common stock on the NASDAQ Global Select Market was $71.35 per share.

Investing in our common stock involves risks. See "Risk Factors" beginning on page S-4 of this prospectus supplement, page 5 of the accompanying prospectus and page 21 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2020 and page 53 of our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2021, as updated by our subsequent filings.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus are truthful or complete. Any representation to the contrary is a criminal offense.

Neither we nor any of the Sales Agents, the Forward Sellers or the Forward Purchasers have authorized anyone to provide any information or to make any representations other than those contained or incorporated by reference into this prospectus supplement, the accompanying prospectus or any free writing prospectus we have prepared. We take no responsibility for, and we cannot assure you as to the reliability of, any other information that others may give you. We are offering to sell, and seeking offers to buy, shares of our common stock only in jurisdictions where offers and sales are permitted. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus, any free writing prospectus prepared by us and the documents incorporated by reference herein is accurate only as of their respective dates or on the date or dates that are specified in those documents regardless of the time of delivery of this prospectus supplement and the accompanying prospectus or any sale of shares of our common stock. Our business, financial condition, liquidity, results of operations and prospects may have changed materially since those dates.

This document contains two parts. The first part is this prospectus supplement, which describes the terms of this offering of common stock and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference. The second part is the accompanying prospectus, which provides more general information, some of which may not apply to this offering. It is important for you to read and consider all information contained in this prospectus supplement and the accompanying prospectus in making your investment decision. You should also read and consider the additional information included in the documents incorporated by reference. See "Where You Can Find More Information" and "Incorporation by Reference" in this prospectus supplement. If the information in this prospectus supplement differs or varies from the information in the accompanying prospectus or the documents incorporated by reference dated prior to the date of this prospectus supplement, you should rely on the information in this prospectus supplement.

Unless otherwise indicated or unless the context requires otherwise, all references in this prospectus supplement to "we", "us", "our", "the Company" and "our company" refer to CyrusOne Inc., a Maryland corporation, together with its consolidated subsidiaries, including CyrusOne LP, a Maryland limited partnership, and CyrusOne GP, a Maryland statutory trust of which we are the sole beneficial owner and sole trustee and which is the sole general partner of our operating partnership ("CyrusOne GP"). Unless otherwise indicated or unless the context requires otherwise, all references to "our operating partnership" or "CyrusOne LP" refer to CyrusOne LP together with its consolidated subsidiaries. CyrusOne Inc., directly or indirectly, owns all the operating partnership units of CyrusOne LP as of December 31, 2020 and has the full, exclusive and complete responsibility for the operating partnership's day-to-day management and control. Effective February 1, 2021, we reorganized CyrusOne LP to classify the partnership as a regarded entity under the provisions of the Internal Revenue Code of 1986, as amended (the "Code").

This prospectus supplement and the accompanying prospectus dated May 3, 2019 are part of the Registration Statement (Registration No. 333-231203) that we filed with the U.S. Securities and Exchange Commission ("SEC") on May 3, 2019, using a "shelf" registration process.

This prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein contain forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended (the "Exchange Act"). We intend such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995 and include this statement for purposes of complying with these safe harbor provisions.

In particular, statements pertaining to our capital resources, portfolio performance, financial condition and results of operations contain certain forward-looking statements. Likewise, all of our statements regarding anticipated growth in our funds from operations and anticipated market conditions, demographics and results of operations are forward-looking statements. You can identify forward-looking statements by the use of forward-looking terminology such as "believes", "expects", "may", "will", "should", "seeks", "approximately", "intends", "plans", "estimates" or "anticipates" or the negative of these words and phrases or similar words or phrases that are predictions of or indicate future events or trends and that do not relate solely to historical matters. You can also identify forward-looking statements by discussions of strategy, plans or intentions.

Forward-looking statements involve numerous risks and uncertainties and you should not rely on them as predictions of future events. Forward-looking statements depend on assumptions, data or methods that may be incorrect or imprecise and we may not be able to realize them. Should one or more of these risks or uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those anticipated, estimated or projected.

The following factors, among others, could cause actual results and future events to differ materially from those set forth or contemplated in the forward-looking statements:

While forward-looking statements reflect our good faith beliefs, they are not guarantees of future performance. For a further discussion of these and other factors that could impact our future results, performance or transactions, see the sections in this prospectus supplement and the accompanying prospectus entitled "Risk Factors", including the risks incorporated herein and therein from our most recent Annual Report on Form 10-K for the fiscal year ended December 31, 2020, and our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2021, as updated by our subsequent filings. Given these risks and uncertainties, investors should not place undue reliance on forward-looking statements as a prediction of actual results. We disclaim any obligation other than as required by law to publicly update or revise any forward-looking statement to reflect changes in underlying assumptions or factors or for new information, data or methods, future events or other changes.

We are subject to the information and reporting requirements of the Exchange Act, and, accordingly, file annual, quarterly and periodic reports, proxy statements and other information with the SEC.

We have filed with the SEC a registration statement on Form S-3, including exhibits and schedules filed with the registration statement of which this prospectus supplement is a part, under the Securities Act with respect to the shares of our common stock registered hereby. This prospectus supplement and the accompanying prospectus do not contain all of the information set forth in the registration statement and exhibits and schedules to the registration statement. For further information with respect to our company and our shares of common stock registered hereby, reference is made to the registration statement, including the exhibits and schedules to the registration statement. Statements contained in this prospectus supplement and the accompanying prospectus as to the contents of any contract or other document referred to in this prospectus supplement and the accompanying prospectus are not necessarily complete and, where that contract is an exhibit to the registration statement, each statement is qualified in all respects by the exhibit to which the reference relates.

Our SEC filings, including our registration statement, are also available to you, free of charge, on the SEC's website at www.sec.gov. Our SEC filings are also available through the "Investors—SEC Filings" tab of our website at www.cyrusone.com. The information contained on or linked to or from our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus and should not be considered part of this prospectus supplement or the accompanying prospectus.

The SEC allows us to "incorporate by reference" certain information into this prospectus supplement from certain documents that we filed with the SEC prior to the date of this prospectus supplement. By incorporating by reference, we are disclosing important information to you by referring you to documents we have filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus supplement, except for information incorporated by reference that is modified or superseded by information contained in this prospectus supplement or in any other subsequently filed document that also is incorporated by reference herein. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to be part of this prospectus supplement. These documents contain important information about us, our business and our finances. The following documents previously filed with the SEC are incorporated by reference into this prospectus supplement except for any document or portion thereof deemed to be "furnished" and not filed in accordance with SEC rules:

We also incorporate by reference all documents we may file with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act on or after the date we file this prospectus supplement, except for any document or portion thereof deemed to be "furnished" and not filed in accordance with SEC rules.

The information relating to us contained in this prospectus supplement does not purport to be comprehensive and should be read together with the information contained in the documents incorporated or deemed to be incorporated by reference herein.

If you request, either orally or in writing, we will provide you with a copy of any or all documents that are incorporated by reference herein. Such documents will be provided to you free of charge, but will not contain any exhibits, unless those exhibits are incorporated by reference into the document. Requests can be made by writing to Investor Relations at 2850 N. Harwood St., Suite 2200, Dallas, Texas 75201 or by telephone at (972) 350-0060. The documents may also be accessed on our website under the "Investors—SEC Filings" tab at www.cyrusone.com. Information contained on or linked to or from our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus and should not be considered part of this prospectus supplement or the accompanying prospectus.

SUMMARY

The following summary contains information about us and the offering. It does not contain all of the information that may be important to you in making a decision to purchase the common stock. For a more complete understanding of us and the common stock, we urge you to read this entire prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein carefully, including the "Risk Factors" section and the financial statements and the notes to those statements incorporated by reference herein. See "Where You Can Find More Information" and "Incorporation by Reference" in this prospectus supplement.

Our Company

We are a fully integrated, self-managed data center real estate investment trust ("REIT") that owns, operates and develops enterprise-class, carrier-neutral, multi-tenant and single-tenant data center properties. Our data centers are generally purpose-built facilities with redundant power and cooling. They are not network specific and enable customer connectivity to a range of telecommunication carriers. We provide mission-critical data center real estate assets that protect and ensure the continued operation of information technology ("IT") infrastructure for approximately 1,000 customers in 54 data centers, including one recovery center in 16 markets (11 cities in the U.S.; London, U.K.; Singapore; Frankfurt, Germany; Amsterdam, The Netherlands and Dublin, The Republic of Ireland).

We provide mission-critical data center real estate assets that protect and ensure the continued operation of IT infrastructure for our customers. We provide twenty-four hours-a-day, seven-days-a-week security guard monitoring with customizable security features. Our goal is to be the preferred global data center provider to hyperscale cloud companies and to the global Fortune 1000 enterprises. Currently, our customers include 191 of the Fortune 1000 companies and nearly half of the Fortune 20 or private or foreign enterprises of equivalent size, together representing approximately 79% of our annualized rent as of December 31, 2020. Our growth over the past 16 years has made us the third-largest data center provider in the U.S. based on the National Association of Real Estate Investment Trusts REITWatch report as of November 30, 2020.

We cultivate long-term strategic relationships with our customers and provide them with solutions for their data center facilities and IT infrastructure challenges. We provide high-quality colocation with robust connectivity and the flexibility for customers to scale for future growth. Our offerings provide flexibility, reliability and security delivered through a tailored, customer service focused platform that is designed to foster long-term relationships. We focus on technology and large cloud computing customers that are expanding their data needs rapidly in the public and private cloud environments to provide them with solutions that address their current and future needs. Our facilities and construction design allow us to offer flexibility in density and power resiliency, and the opportunity for expansion as our customers' needs grow. Our network of 55 owned or leased data centers and investments with other colocation providers enable us to provide our customers with solutions in the United States and Europe. The platform enables high-performance, low-cost data transfer and accessibility for customers.

Corporate Information

Our principal executive offices are located at 2850 N. Harwood St., Suite 2200, Dallas, Texas 75201. Our telephone number is (972) 350-0060.

The Offering

The following summary contains basic information about this offering. It does not contain all the information that is important to you. You should read this prospectus supplement, the accompanying prospectus and the documents incorporated by reference carefully before making an investment decision.


Issuer		CyrusOne Inc.
Common stock offered		Shares of our common stock with an aggregate gross sales price of up to $750,000,000. The shares of our common stock offered pursuant to this prospectus supplement and the accompanying prospectus include newly issued shares that may be offered and sold by us to or through the Sales Agents, acting as our sales agents or as principal, and borrowed shares of our common stock that may be offered and sold by the Forward Purchasers through their respective Forward Sellers.
Use of proceeds		We intend to contribute the net proceeds from any sales of shares of our common stock to or through the Sales Agents and the net cash proceeds from the settlement of any forward sale agreements to our operating partnership in exchange for an equivalent number of newly issued operating partnership units in accordance with the partnership agreement of our operating partnership. Our operating partnership intends to use the proceeds contributed by us for general corporate purposes, which may include funding future acquisitions, investments or capital expenditures and repaying outstanding indebtedness, including borrowings under our senior unsecured revolving credit facility (the "Revolving Loans").
		We will not initially receive any proceeds from any sale of borrowed shares of our common stock by a Forward Purchaser in connection with any forward sale agreement as a hedge of such forward sale agreement. For additional information, see "Plan of Distribution—Sales Through Forward Sellers".


Accounting treatment of any forward sales		In the event that we enter into any forward sale agreements, before the issuance of shares of our common stock, if any, upon settlement of such forward sale agreement, we expect that the shares issuable upon settlement of such forward sale agreement will be reflected in our diluted earnings per share using the treasury stock method. Under this method, the number of shares of our common stock used in calculating diluted earnings per share is deemed to be increased by the excess, if any, of the number of shares of our common stock that would be issued upon full physical settlement of such forward sale agreement over the number of shares of our common stock that could be purchased by us in the market (based on the average market price during the relevant forward hedge selling period specified in such forward sale agreement) using the proceeds receivable upon full physical settlement (based on the adjusted forward sale price at the end of the relevant reporting period). Consequently, we anticipate there will be no dilutive effect on our earnings per share prior to physical or net share settlement of such forward sale agreement except during periods when the average market price of shares of our common stock is above the applicable adjusted forward sale price, which is subject to increase or decrease based on the federal funds rate, less a spread to be mutually agreed by us and the applicable Forward Purchaser, and subject to decrease by amounts related to expected dividends on shares of our common stock during the term of such forward sale agreement. However, if we decide to physically settle or net share settle any forward sale agreement, delivery of shares of our common stock to the applicable Forward Purchaser on any such physical settlement or net share settlement date would result in dilution to our earnings per share and other reported per share measures.
NASDAQ symbol		CONE
Transfer agent and registrar		Computershare Trust Company N.A.
Risk factors		Investing in our common stock involves a high degree of risk. See "Risk Factors" beginning on page S-4 of this prospectus supplement and all other information included or incorporated by reference into this prospectus supplement and the accompanying prospectus (including the risks incorporated by reference from our Annual Report on Form 10-K for the fiscal year ended December 31, 2020 and our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2021, as such risk factors may be amended, supplemented or superseded by our subsequent filings with the SEC) for a discussion of the factors you should carefully consider before deciding to invest in our common stock.

An investment in our common stock involves risks. You should carefully consider the risk factors incorporated by reference from our Annual Report on Form 10-K for the fiscal year ended December 31, 2020 and our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2021, the risks discussed below and the other information contained in this prospectus supplement, the accompanying prospectus and the documents we incorporate by reference herein (as such risk factors may be amended, supplemented or superseded by our subsequent filings with the SEC) before purchasing shares of our common stock. Some statements in this prospectus supplement, including statements in the following risk factors, constitute forward-looking statements. Please refer to the section entitled "Special Note Regarding Forward-Looking Statements".

Our cash available for distribution to stockholders may not be sufficient to make distributions at expected levels, and we may need to borrow in order to make such distributions; consequently, we may not be able to make such distributions in full.

If cash available for distribution generated by our assets is less than our estimate or if such cash available for distribution decreases in future periods from expected levels, our inability to make the expected distributions could result in a decrease in the market price of our common stock. Distributions made by us will be authorized and determined by our board of directors in its sole discretion out of funds legally available therefor and will be dependent upon a number of factors, including restrictions under applicable law and our capital requirements. We may not be able to make or sustain distributions in the future. To the extent that we decide to make distributions in excess of our current and accumulated earnings and profits, such distributions would generally be considered a return of capital for U.S. federal income tax purposes to the extent of the holder's adjusted tax basis in its shares. A return of capital is not taxable, but it has the effect of reducing the holder's adjusted tax basis in its investment. To the extent that distributions exceed the adjusted tax basis of a holder's shares, they will be treated as gain from the sale or exchange of such stock. See "U.S. Federal Income Tax Considerations—Taxation of Stockholders—Taxation of Taxable U.S. Stockholders—Distributions" in the accompanying prospectus. If we borrow to fund distributions, our future interest costs would increase, thereby reducing our earnings and cash available for distribution from what they otherwise would have been.

We have significant outstanding indebtedness that involves significant debt service obligations, limits our operational and financial flexibility, exposes us to interest rate fluctuations and exposes us to the risk of default under our debt obligations.

As of December 31, 2020, we had a total combined indebtedness, including finance lease liabilities and operating lease liabilities, of approximately $3.7 billion. As of December 31, 2020, we have the ability to borrow up to an additional approximately $1.0 billion under our existing senior unsecured credit agreement, dated as of March 29, 2018, as amended (the "Amended Credit Agreement"), net of outstanding letters of credit of approximately $10.8 million, subject to satisfying certain financial tests. Our Amended Credit Agreement, also contains an accordion feature that, as of December 31, 2020, allows the operating partnership to request an increase in the total commitment by up to $1.5 billion. There are no limits on the amount of indebtedness we may incur other than limits contained in the indentures governing our senior notes, the Amended Credit Agreement or future agreements that we may enter into or as may be set forth in any policy limiting the amount of indebtedness we may incur adopted by our board of directors. A substantial level of indebtedness could have adverse consequences

for our business, financial condition, results of operations, cash flows and ability to pay dividends as well as the market price of our common stock because it could, among other things:

Future offerings of debt, which would be senior to our common stock upon liquidation, and/or preferred equity securities, which may be senior to our common stock for purposes of distributions or upon liquidation, may adversely affect the market price of our common stock.

In the future, we may attempt to increase our capital resources by making additional offerings of debt or preferred equity securities, including medium-term notes, trust preferred securities, senior or subordinated notes and preferred stock. Upon liquidation, holders of our debt securities and shares of preferred stock and lenders with respect to other borrowings will receive distributions of our available assets prior to the holders of our common stock. Additional equity offerings may dilute the holdings of our existing stockholders or reduce the market price of our common stock, or both. Holders of our common stock are not entitled to preemptive rights or other protections against dilution. Our preferred stock, if issued, could have a preference on liquidating distributions or a preference on distribution payments that could limit our ability to make a distribution to the holders of our common stock. Because our decision to issue securities in any future offering will depend on market conditions and other factors beyond our control, we cannot predict or estimate the amount, timing or nature of our future offerings. Thus, our stockholders bear the risk of our future offerings reducing the market price of our common stock and diluting their stock holdings in us.

Increases in market interest rates may cause potential investors to seek higher dividend yields and therefore reduce demand for our common stock and result in a decline in our stock price.

One of the factors that may influence the price of our common stock is the dividend yield on our common stock (the amount of dividends as a percentage of the price of our common stock) relative to market interest rates. An increase in market interest rates, which are currently at low levels relative to historical rates, may lead prospective purchasers of our common stock to expect a higher dividend yield, which we may be unable or choose not to provide. Higher interest rates would likely increase our borrowing costs and potentially decrease the cash available for distribution. Thus, higher market interest rates could cause the market price of our common stock to decline.

The number of shares available for future sale could adversely affect the market price of our common stock.

We cannot predict whether future issuances of shares of our common stock or the availability of shares of our common stock for resale in the open market will decrease the market price per share of our common stock. Sales of a substantial number of shares of our common stock in the public market, or the perception that such sales might occur, could adversely affect the market price of the shares of our common stock. For example we have previously entered into forward sale agreements in connection with the Prior Offering. As of May 3, 2021, we remained obligated to issue (subject to our right to elect cash settlement or net share settlement and subject to adjustment in accordance with the terms of the relevant forward sale agreements) a total of 5.4 million shares of our common stock pursuant to forward sale agreements on settlement dates specified by us on or prior to dates ranging from May 14, 2021 to November 6, 2021. Physical settlement of these forward sale agreements or other forward sale agreements in the future have resulted or will result in dilution to our earnings per share. In addition, we have registered shares of common stock that were reserved for issuance under our Restated 2012 Long Term Incentive Plan and under our 2014 Employee Stock Purchase Plan, and these shares can generally be freely sold in the public market, assuming any applicable restrictions and vesting requirements are satisfied. If any or all of these holders cause a large number of their shares to be sold in the public market, the sales could reduce the trading price of our common stock and could impede our ability to raise future capital on terms acceptable to us or at all.

For a discussion of potential dilution resulting from any forward sale agreement entered into under this prospectus supplement, see "—Risks Related to Forward Sale Agreements—Settlement provisions contained in any forward sale agreement subject us to certain risks".

The market price of our common stock may be volatile. In addition, the trading volume in our common stock may fluctuate and cause significant price variations to occur. If the market price of our common stock declines significantly, a holder may be unable to resell shares at a profit or at all. We cannot provide any assurance that the market price of our common stock will not fluctuate or decline significantly in the future.

Some of the factors that could negatively affect the market price of our common stock or result in fluctuations in the price or trading volume of our common stock include:

Our earnings and cash distributions will affect the market price of shares of our common stock.

To the extent that the market value of a REIT's equity securities is based primarily upon market perception of the REIT's growth potential and its current and potential future cash distributions, whether from operations, sales, acquisitions, development or refinancing and is secondarily based upon the value of the underlying assets, shares of our common stock may trade at prices that are higher or lower than the net asset value per share. To the extent we retain operating cash flow for investment purposes, working capital reserves or other purposes rather than distributing the cash flow to stockholders, these retained funds, while increasing the value of our underlying assets, may negatively impact the market price of our common stock. Our failure to meet market expectations with regard to future earnings and cash distributions would likely adversely affect the market price of our common stock.

Changes to U.S. federal income tax laws could materially and adversely affect us and our stockholders.

The present U.S. federal income tax treatment of REITs and their shareholders may be modified, possibly with retroactive effect, by legislative, judicial or administrative action at any time, which could affect the U.S. federal income tax treatment of an investment in our shares. The U.S. federal income tax rules, including those dealing with REITs, are constantly under review by persons involved in the legislative process, the IRS and the U.S. Treasury Department, which results in statutory changes as well as frequent revisions to regulations and interpretations.

Settlement provisions contained in any forward sale agreement subject us to certain risks.

Each Forward Purchaser will have the right to accelerate the settlement of the shares of our common stock underlying any forward sale agreement it has entered into with us, in whole or in part (except with respect to events specified in (1) and (5) below, where accelerated settlement shall not exceed the portion of shares of our common stock whose settlement would address the relevant event or that is affected by the relevant event, plus, in certain cases, a de minimis number of additional shares) and require us to physically settle on a date specified by the Forward Purchaser if, among other events:

A Forward Purchaser's decision to exercise its right to accelerate the settlement of any forward sale agreement will be made irrespective of our interests, including our need for capital. In such cases, we could be required to issue and deliver shares of our common stock under the physical settlement provisions or, if we so elect and the relevant Forward Purchaser so permits our election, net share settlement provisions of the applicable forward sale agreement irrespective of our capital needs, which would result in dilution to our earnings per share, return on investment and dividends per share.

We expect that any forward sale agreement will be physically settled by delivery of shares of our common stock, unless we elect to cash settle or net share settle the forward sale agreement, subject to the satisfaction of certain conditions. Upon physical settlement or, if we so elect, net share settlement of any forward sale agreement, delivery of shares of our common stock in connection with such physical settlement or, to the extent we are obligated to deliver shares of our common stock, net share settlement will result in dilution to our earnings per share, return on investment and dividends per share. If we elect cash settlement or net share settlement with respect to all or a portion of the shares of our common stock underlying any forward sale agreement, we expect the applicable Forward Purchaser (or an affiliate thereof) to purchase a number of shares of our common stock in secondary market transactions over an unwind period necessary to satisfy its or its affiliate's obligation to return the shares of our common stock borrowed in connection with sales of shares of our common stock under this prospectus supplement (adjusted, in the case of net share settlement, by any shares deliverable by us under the applicable forward sale agreement).

In addition, the purchase of shares of our common stock in connection with any Forward Purchaser or its affiliate unwinding its hedge positions could cause the price of shares of our common stock to increase over such time (or prevent a decrease over such time), thereby increasing the amount of cash we would owe to such Forward Purchaser (or decreasing the amount of cash such Forward Purchaser would owe us) upon a cash settlement of the applicable forward sale agreement or the number of shares of our common stock we would deliver to such Forward Purchaser (or decreasing the number of shares of our common stock such Forward Purchaser would deliver to us) upon net share settlement of such forward sale agreement.

The forward sale price we expect to receive upon physical settlement of any forward sale agreement will be subject to adjustment on a daily basis based on a floating interest rate factor equal to the federal funds rate less a spread to be mutually agreed by us and the applicable Forward Purchaser, and will be decreased on certain dates based on amounts related to expected dividends on shares of our common stock during the term of such forward sale agreement. If the federal funds rate

is less than the spread under such forward sale agreement on any day, the interest factor will result in a daily reduction of the applicable forward sale price. If the market value of shares of our common stock during the relevant valuation period under any forward sale agreement is above the relevant forward sale price, in the case of cash settlement, we would pay the relevant Forward Purchaser an amount in cash equal to the difference or, in the case of net share settlement, we would deliver to the relevant Forward Purchaser a number of shares of our common stock having a value equal to the difference. Thus, we could be responsible for a potentially substantial cash or stock payment. If the market value of shares of our common stock during the relevant valuation period under any forward sale agreement is below the relevant forward sale price, in the case of cash settlement, we would be paid the difference in cash by the relevant Forward Purchaser or, in the case of net share settlement, we would receive from the relevant Forward Purchaser a number of shares of our common stock having a value equal to the difference. See "Plan of Distribution—Sales Through Forward Sellers" for information on the forward sale agreements.

In certain bankruptcy, insolvency or reorganization events, any forward sale agreements will automatically terminate, and we would not receive the expected proceeds from any forward sale of our common stock.

If we file for or a regulatory authority with jurisdiction over us institutes, or we consent to a proceeding seeking a judgment in bankruptcy or insolvency or any other relief under any bankruptcy or insolvency law or other similar law affecting creditors' rights, or we or a regulatory authority with jurisdiction over us presents a petition for our winding-up or liquidation, and we consent to such a petition, any forward sale agreement that is then in effect will automatically terminate. If any such forward sale agreement so terminates, we would not be obligated to deliver to the relevant Forward Purchaser any shares of our common stock not previously delivered, and the Forward Purchaser would be discharged from its obligation to pay the relevant forward sale price per share in respect of any shares of our common stock not previously settled under the applicable forward sale agreement. Therefore, to the extent there are any shares of our common stock with respect to which any forward sale agreement has not been settled at the time of the commencement of any such bankruptcy or insolvency proceedings, we would not receive the relevant forward sale price per share in respect of those shares of our common stock.

The shares of our common stock offered pursuant to this prospectus supplement and the accompanying prospectus include newly issued shares that may be offered and sold by us to or through the Sales Agents, acting as our sales agents or as principals, and borrowed shares of our common stock that may be offered and sold by the Forward Purchasers through their respective Forward Sellers. We intend to contribute the net proceeds from any sales of shares of our common stock to or through the Sales Agents and the net cash proceeds from the settlement of any forward sale agreements to our operating partnership in exchange for an equivalent number of newly issued operating partnership units in accordance with the partnership agreement of our operating partnership. Our operating partnership intends to use the proceeds contributed by us for general corporate purposes, which may include funding future acquisitions, investments or capital expenditures and repaying outstanding indebtedness, including the Revolving Loans.

We will not initially receive any proceeds from any sale of borrowed shares of our common stock by a Forward Purchaser in connection with a forward sale agreement as a hedge of such forward sale agreement. In the event of full physical settlement of a forward sale agreement, which we expect to occur on or prior to the maturity date of the forward sale agreement, we expect to receive aggregate cash proceeds equal to the product of the forward sale price under the forward sale agreement and the number of shares of our common stock underlying the forward sale agreement, subject to the price adjustment and other provisions of the forward sale agreement. If, however, we elect to cash settle or net share settle any forward sale agreement, we would expect to receive an amount of proceeds that is significantly lower than the product set forth in the preceding sentence (in the case of any cash settlement) or will not receive any proceeds (in the case of any net share settlement), and we may owe cash (in the case of any cash settlement) or shares of our common stock (in the case of any net share settlement) to the relevant Forward Purchaser.

As of March 31, 2021, we have approximately $1.2 billion of borrowings outstanding under the Amended Credit Agreement, consisting of $386.3 million of borrowings under our senior unsecured revolving credit facility (consisting of $351.8 million of borrowings denominated in Euros and $34.5 million of borrowings denominated in British pound sterling), $100 million under our senior unsecured term loans due 2023 and $700 million under our senior unsecured term loans due 2025. As of March 31, 2021, borrowings under the U.S. portion of our senior unsecured revolving credit facility bear interest at a rate equal to Monthly USD EURIBOR plus 1.00%. Monthly USD LIBOR as of March 31, 2021 was 0.11%. As of March 31, 2021, borrowings under the GBP portion of our senior unsecured revolving credit facility bear interest at a rate equal to Monthly GBP LIBOR plus 1.00%. Monthly GBP LIBOR as of March 31, 2021 was 0.06%. Our existing senior unsecured revolving credit facility is scheduled to mature in March 2024 and includes one twelve-month extension option that, if exercised by our operating partnership, would extend the termination date to March 2025. The borrowings under our senior credit facility that might be repaid with the net proceeds from this offering have been used from time to time for general corporate purposes. Any borrowings under our senior unsecured revolving credit facility that are repaid with the net proceeds from this offering may be reborrowed, subject to customary conditions.

Affiliates of certain of the Sales Agents and Forward Purchasers in this offering are lenders under our senior unsecured revolving credit facility. To the extent that we use a portion of the net proceeds from any sales of our common stock under this prospectus supplement to repay Revolving Loans, the applicable affiliates will receive their proportionate shares of any such amount. See "Plan of Distribution—Relationships".

Forward Seller, shares of our common stock to hedge such Forward Purchaser's exposure under such forward sale agreement. All of the net proceeds from the sale of any such borrowed shares will be paid to the applicable Forward Purchaser (or one or more of its affiliates). Each Forward Purchaser will be either a Sales Agent or an affiliate of a Sales Agent. As a result, a Sales Agent or its affiliate will receive the net proceeds from any sale of borrowed shares of our common stock made in connection with any forward sale agreements.

We have entered into separate sales agreements dated as of May 3, 2021, with each of J.P. Morgan Securities LLC, Barclays Capital Inc., BMO Capital Markets Corp., Credit Agricole Securities (USA) Inc., Deutsche Bank Securities Inc., Fifth Third Securities, Inc., Goldman Sachs & Co. LLC, Jefferies LLC, KeyBanc Capital Markets Inc., Morgan Stanley & Co. LLC, MUFG Securities Americas Inc., RBC Capital Markets, LLC, Stifel, Nicolaus & Company, Incorporated, TD Securities (USA) LLC and Truist Securities, Inc., as the Sales Agents, and, as applicable, the relevant Forward Purchasers, under which we may offer and sell shares of our common stock having an aggregate gross sales price of up to $750,000,000 from time to time through the Sales Agents, acting as our sales agents, or, if applicable, as Forward Sellers, or directly to the Sales Agents acting as principals.

Sales, if any, of shares of our common stock under this prospectus supplement and the accompanying prospectus made through the Sales Agents, as our sales agents or as Forward Sellers, may be made (1) in "at the market" offerings (as defined in Rule 415 under the Securities Act) by means of ordinary brokers' transactions at market prices prevailing at the time of sale, including sales made on the NASDAQ Global Select Market, sales made to or through market makers and sales made through other securities exchanges or electronic communications networks and (2) in such privately negotiated transactions, which may include block trades, as we and any Sales Agent or Forward Seller may agree. As our sales agents, the Sales Agents will not engage in any transactions that stabilize our common stock.

The sales agreements with each of J.P. Morgan Securities LLC, Barclays Capital Inc., BMO Capital Markets Corp., Credit Agricole Securities (USA) Inc., Deutsche Bank Securities Inc., Fifth Third Securities, Inc., Goldman Sachs & Co. LLC, Jefferies LLC, KeyBanc Capital Markets Inc., Morgan Stanley & Co. LLC, MUFG Securities Americas Inc., RBC Capital Markets, LLC, Stifel, Nicolaus & Company, Incorporated, TD Securities (USA) LLC and Truist Securities, Inc. contemplate that, in addition to the issuance and sale by us of shares of our common stock to or through the relevant Sales Agents acting as our sales agents, we may enter into separate forward sale agreements with any of, respectively, JPMorgan Chase Bank, National Association, Barclays Bank PLC, Bank of Montreal, Crédit Agricole Corporate and Investment Bank, Deutsche Bank AG, London Branch, Goldman Sachs & Co. LLC, Jefferies LLC, KeyBanc Capital Markets Inc., Morgan Stanley & Co. LLC, MUFG Securities EMEA plc, Royal Bank of Canada, The Toronto-Dominion Bank and Truist Bank or one of their respective affiliates, each as a Forward Purchaser. If we enter into a forward sale agreement with any Forward Purchaser, we expect that such Forward Purchaser, acting in accordance with the mutually accepted instructions related to such forward sale agreement, will attempt to borrow and sell, through the relevant Sales Agent, acting as sales agent for such Forward Purchaser (i.e., as Forward Seller), shares of our common stock to hedge such Forward Purchaser's exposure under such forward sale agreement. Only Sales Agents that are, or are affiliated with, Forward Purchasers will act as Forward Sellers.

None of the Sales Agents, whether acting as our sales agent or as a Forward Seller, if applicable, is required to sell any specific number or dollar amount of shares of our common stock, but each has agreed to use its commercially reasonable efforts, consistent with its normal trading and sales practices and applicable law and regulations, to sell, on the terms and subject to the conditions of the relevant sales agreement, shares of our common stock on terms agreed upon by such Sales Agent, us and, in the case of shares offered through such Sales Agent as Forward Seller, the relevant Forward Purchaser from time to time. The shares of our common stock offered and sold through the Sales Agents, as our sales agents or as Forward Sellers, pursuant to the sales agreement will be offered and sold through only one Sales Agent on any given trading day.

In no event will the aggregate gross sales price of shares of our common stock sold by us to or through the Sales Agents, acting as our sales agents or as principals, and by the Forward Purchasers

through the applicable Sales Agents, acting as Forward Sellers in connection with any forward sale agreements, exceed $750,000,000.

Unless otherwise set forth in a prospectus supplement, we will report at least quarterly the number of shares of our common stock sold to or through the Sales Agents (including as Forward Sellers) under the sales agreements during the relevant quarterly period and the aggregate net proceeds to us in connection with such sales, together with any other information we reasonably believe is required to comply with the Securities Act and Exchange Act with respect to such sales.

Under each of the sales agreements, if we, a Sales Agent or a Forward Purchaser believe that the exemptive provisions set forth in Rule 101(c)(1) of Regulation M under the Exchange Act (applicable to "actively-traded securities") are not satisfied with respect to us or shares of our common stock, that party will promptly notify the others, and sales of shares of our common stock under the applicable sales agreement, terms agreement and forward sales agreement will be suspended until that or other exemptive provisions have been satisfied in the judgment of the applicable Sales Agent and us.

The offering of shares of our common stock pursuant to any sales agreement will terminate upon the earlier of (1) the sale of shares of our common stock subject to the sales agreements (including shares sold by us to or through the Sales Agents and borrowed shares sold through the Sales Agents acting as Forward Sellers) having an aggregate gross sales price of $750,000,000 and (2) with respect to a particular sales agreement, the termination of such sales agreement by us or by the applicable Sales Agent as permitted therein.

Shares of our common stock are listed on the NASDAQ Global Select Market under the trading symbol "CONE".

Because there is no minimum offering amount contemplated by the sales agreements, commissions and net proceeds to us from the sale of shares of our common stock under this prospectus supplement and the accompanying prospectus, if any, are not determinable at this time. The estimated offering expenses payable by us, exclusive of the commissions to the Sales Agents, are approximately $550,000. We have also agreed to reimburse the Sales Agents for certain of their expenses in an amount up to $10,000. The remaining proceeds from the sale of shares of our common stock under this prospectus supplement and the accompanying prospectus, after deducting any commissions, discounts and expenses, and any transfer taxes or similar fees, taxes or charges imposed by any governmental or self-regulatory organization in connection with such sales, will constitute the net proceeds from the sale of such shares. However, as described below under "—Sales Through Forward Sellers", we will not initially receive any proceeds from the sale of shares of our common stock borrowed by a Forward Purchaser and sold through the relevant Sales Agent, acting as Forward Seller.

Each Sales Agent will offer the shares of our common stock subject to the terms and conditions of the applicable sales agreement on an agented basis or as otherwise agreed between us and each Sales Agent. We will designate the maximum amount and maximum aggregate offering price of shares of our common stock to be sold through each Sales Agent and the minimum price per share at which each share of our common stock may be sold on any trade date. Subject to the terms and conditions stated in the applicable sales agreement, each Sales Agent will use its commercially reasonable efforts, consistent with its normal trading and sales practices and applicable law and regulations, to sell the shares offered as our sales agent. The Sales Agents may not sell common stock if the sales cannot be effected at or above the minimum price designated by us from time to time. We or any Sales Agent may suspend the offering of shares of our common stock to be sold through such Sales Agent as our sales agent or as principal upon proper notice to the other party and subject to other conditions.

Each Sales Agent will receive from us a mutually agreed commission that will not exceed, but may be lower than, 2.0% of the gross sales price of any shares sold through such Sales Agent, as our sales

agent, pursuant to the applicable sales agreement. Each Sales Agent will provide written confirmation to us following the close of trading on the NASDAQ Global Select Market each day in which shares of our common stock are sold by such Sales Agent for us under the applicable sales agreement. Each confirmation will include the number of shares of our common stock sold on that day, the gross sales proceeds of those sales, the compensation payable by us to the applicable Sales Agent and the proceeds to us net of that compensation.

We expect that settlement for sales of shares of our common stock will occur, unless we and the applicable Sales Agent agree otherwise, on the second business day (other than a day on which the NASDAQ Global Select Market is scheduled to close prior to its regular weekday closing time) following the trade date on which any sales are made in return for payment of the proceeds to us net of compensation paid by us to such Sales Agent. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

If we enter into a forward sale agreement with any Forward Purchaser, we expect that such Forward Purchaser, acting in accordance with the mutually accepted instructions related to such forward sale agreement, will attempt to borrow and sell, through the relevant Sales Agent, acting as sales agent for such Forward Purchaser (i.e., as Forward Seller), shares of our common stock to hedge such Forward Purchaser's exposure under such forward sale agreement. No Forward Purchaser is obligated to enter into a forward sale agreement with us unless it and the relevant Forward Seller each agrees to the terms we propose for such forward sale transaction in our instructions delivered in accordance with the relevant sales agreement (as such instructions may be modified upon mutual consent of such Forward Purchaser, Forward Seller and us).

In connection with any forward sale agreement and our instructions accepted by the relevant Forward Purchaser and Forward Seller (as such instructions may have been modified upon mutual consent of such Forward Purchaser, Forward Seller and us), such Forward Purchaser will use its commercially reasonable efforts to borrow or cause its affiliate to borrow, offer and sell through the relevant Sales Agent as Forward Seller the applicable shares of our common stock to hedge the Forward Purchaser's exposure under the relevant forward sale agreement, and such Sales Agent as Forward Seller will use its commercially reasonable efforts, consistent with its normal trading and sales practices and applicable law and regulations, to sell such shares of our common stock, on the terms and subject to the conditions set forth in the relevant sales agreement and forward sale agreement. Such instructions will specify the target number and maximum aggregate offering price of shares of our common stock to be sold by it as Forward Seller and will also specify that such Sales Agent shall not sell such shares of common stock if the sales cannot be effected at or above a price designated by us. We or the applicable Sales Agent or Forward Purchaser may at any time immediately suspend the offering of shares of our common stock through such Sales Agent, as Forward Seller, upon proper notice to the other party and subject to other conditions.

Each Sales Agent that acts as a Forward Seller will receive from us a mutually agreed commission in the form of a reduction to the initial forward price under the related forward sale agreement that will not exceed, but may be lower than, 2.0% of the gross sales price of the borrowed shares sold

through such Sales Agent, acting as Forward Seller, during the applicable forward hedge selling period for such shares (which gross sales price will be adjusted for daily accruals based on a floating interest rate and specified amounts related to expected dividends on shares of our common stock if an "ex-dividend" date occurs during such forward hedge selling period). We sometimes refer to this commission as the "forward selling commission".

We expect that settlement between a Forward Purchaser and the relevant Sales Agent, as Forward Seller, for sales of borrowed shares of our common stock, as well as settlement between such Sales Agent and buyers of such shares in the market, will occur on the second business day (other than a day on which the NASDAQ Global Select Market is scheduled to close prior to its regular weekday closing time) following the respective dates on which any such sales are made, or such other date as may be agreed upon by the relevant parties. There is no arrangement for funds to be received in escrow, trust or similar arrangement. The obligations of a Sales Agent, acting as Forward Seller, and the relevant Forward Purchaser under the sales agreement are subject to a number of conditions, which such Sales Agent and Forward Purchaser may waive in their sole discretion.

We currently expect to fully physically settle each forward sale agreement, if any, with the relevant Forward Purchaser on one or more dates specified by us on or prior to the maturity date of such forward sale agreement, although we will generally have the right, subject to certain exceptions, to elect cash settlement or net share settlement instead of physical settlement for any of the shares we have agreed to sell under such forward sale agreement. If we elect or are deemed to have elected to physically settle all or any portion of any forward sale agreement by delivering shares of our common stock, we will receive aggregate cash proceeds from the relevant Forward Purchaser equal to the product of (1) the then-applicable forward price per share under such forward sale agreement and (2) the number of shares of our common stock as to which we have elected or are deemed to have elected physical settlement, subject to the price adjustment and other provisions of such forward sale agreement. The initial forward price per share under each forward sale agreement will equal the product of (x) an amount equal to 100% minus the applicable forward selling commission and (y) the volume weighted average price per share at which the borrowed shares of our common stock were sold pursuant to the sales agreement by the relevant Sales Agent, acting as Forward Seller, during the applicable forward hedge selling period for such shares to hedge the relevant Forward Purchaser's exposure under such forward sale agreement (subject to certain adjustments to such gross sales price for daily accruals based on a floating interest rate and specified amounts related to expected dividends on shares of our common stock having an "ex-dividend" date during such forward hedge selling period). Thereafter, each forward sale agreement will provide that the forward price will be subject to adjustment on a daily basis based on a floating interest rate factor equal to the federal funds rate less a spread to be mutually agreed by us and the applicable Forward Purchaser, and will be decreased based on specified amounts related to expected dividends on shares of our common stock during the term of applicable forward sale agreement. If the federal funds rate is less than the spread on any day, the interest factor will result in a daily reduction of the applicable forward sale price. We will not initially receive any proceeds from any sale of shares of our common stock borrowed by a Forward Purchaser and sold through a Forward Seller, and all of such proceeds will be paid to the relevant Forward Purchaser (or one or more of its affiliates).

Before settlement of any forward sale agreement, we expect that shares issuable upon settlement of the applicable forward sale agreement will be reflected in our diluted earnings per share using the treasury stock method. Under this method, the number of shares of our common stock used in calculating diluted earnings per share is deemed to be increased by the excess, if any, of the number of shares of our common stock that would be issued upon full physical settlement of such forward sale agreement over the number of shares of our common stock that could be purchased by us in the market (based on the average market price during the relevant forward hedge selling period specified in such forward sale agreement) using the proceeds receivable upon full physical settlement (based on the adjusted forward sale price at the end of the reporting period). Consequently, we anticipate there

will be no dilutive effect on our diluted earnings per share prior to physical or net share settlement of such forward sale agreement except during periods when the average market price of shares of our common stock is above the applicable adjusted forward sale price. However, if we decide to physically settle or net share settle any forward sale agreement, delivery of shares of our common stock to the applicable Forward Purchaser on any such physical settlement or net share settlement date would result in dilution to our earnings per share and other reported per share measures.

Except under the circumstances described below and set forth in any forward sale agreement, we have the right to elect physical, cash or net share settlement under any forward sale agreement. Although we expect to settle any forward sale agreement entirely by delivering shares of our common stock in connection with full physical settlement, we may, subject to certain conditions, elect cash settlement or net share settlement for all or a portion of our obligations if we conclude it is in our interest to cash settle or net share settle. For example, we may conclude it is in our interest to cash settle or net share settle if we have no then-current use for all or a portion of the proceeds we would receive upon physical settlement. In addition, subject to certain conditions, we may elect to accelerate the settlement of all or a portion of the number of shares of our common stock underlying any forward sale agreement.

In the event we elect to cash settle or net share settle, the settlement amount will be generally related to the product of (1)(a) the market value of shares of our common stock during the valuation period under the applicable forward sale agreement minus (b) the applicable forward sale price; and (2) the number of shares of our common stock underlying the relevant forward sale agreement subject to such cash settlement or net share settlement. If this settlement amount is a negative number, the relevant Forward Purchaser will pay us the absolute value of that amount or deliver to us a number of shares of our common stock having a value equal to the absolute value of such amount. If this settlement amount is a positive number, we will pay the relevant Forward Purchaser that amount or deliver to such Forward Purchaser a number of shares of our common stock having a value equal to such amount. In connection with any cash settlement or net share settlement, we would expect the relevant Forward Purchaser or its affiliate to purchase shares of our common stock in secondary market transactions for delivery to third-party stock lenders in order to close out its, or its affiliate's, hedge position in respect of the applicable forward sale agreement (adjusted, in the case of net share settlement, by any shares deliverable by us under the relevant forward sale agreement). The purchase of shares of our common stock in connection with a Forward Purchaser or its affiliate unwinding its hedge positions could cause the price of shares of our common stock to increase over time (or prevent a decrease over time), thereby increasing the amount of cash we owe to such Forward Purchaser (or decreasing the amount of cash such Forward Purchaser owes us) upon cash settlement or increasing the number of shares of our common stock we are obligated to deliver to such Forward Purchaser (or decreasing the number of shares of our common stock such Forward Purchaser is obligated to deliver to us) upon net share settlement. Any such change could be significant and could result in our receipt of a significant amount of cash or number of shares of our common stock from such Forward Purchaser or require us to pay a significant amount of cash or deliver a significant number of shares of our common stock to such Forward Purchaser. See "Risk Factors—Risks Related to any Forward Sale Agreements".

Each Forward Purchaser will have the right to accelerate the settlement of the shares underlying any forward sale agreement it has entered into with us, in whole or in part (except with respect to events specified in (1) and (5) below, where accelerated settlement shall not exceed the portion of shares whose settlement would address the relevant event or that is affected by the relevant event, plus, in certain cases, a de minimis number of additional shares) and require us to physically settle on a date specified by the Forward Purchaser if, among other events:

Any Forward Purchaser's decision to exercise its right to accelerate the settlement of the relevant forward sale agreement will be made irrespective of our need for capital. In such cases, we could be required to issue and deliver shares of our common stock under the physical settlement provisions or, if we so elect and the relevant Forward Purchaser so permits our election, net share settlement provisions of the relevant forward sale agreement irrespective of our capital needs which would result in dilution to our earnings per share, return on investment and dividends per share. In addition, upon certain events of bankruptcy or insolvency relating to us, any forward sale agreements will terminate without further liability of any party. Following any such termination, we would not issue any shares of our common stock and we would not receive any proceeds pursuant to any forward sale agreement. See "Risk Factors—Risks Related to Forward Sale Agreements".

The descriptions of certain provisions of the sales agreements and the forward sale agreements appearing above and elsewhere in this prospectus supplement are not complete and are subject to, and qualified in their entirety by reference to, the terms and provisions of such sales agreements and forward sale agreements. A form of a forward sale agreement is included as an exhibit to a form of a sales agreement, which has been or will be filed as an exhibit to a document incorporated by reference in the accompanying prospectus and may be obtained as described under "Where You Can Find More Information" in the accompanying prospectus.

The Sales Agents and Forward Purchasers are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, principal investment, hedging, financing and brokerage activities. The Sales Agents, Forward Purchasers and their respective affiliates have in the past performed commercial banking, investment banking and advisory services for us from time to time for which they have received customary fees and reimbursement of expenses and may, from time to time, engage in transactions with and perform services for us in the ordinary course of their business for which they may receive customary fees and reimbursement of expenses. In the ordinary course of their various business activities, the Sales Agents, Forward Purchasers and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative

securities), commodities, currencies and other financial instruments (which may include bank loans and/or credit default swaps) for their own account and for the accounts of their customers and may at any time hold long and short positions in such securities and instruments. The Sales Agents, Forward Purchasers and their respective affiliates may also communicate independent investment recommendations, market color or trading ideas and/or publish or express independent research views in respect of such assets, securities or instruments and may at any time hold, or recommend to clients that they should acquire, long and/or short positions in such assets, securities and instruments. Such investment and securities activities may involve our securities and instruments.

Affiliates of each of the Sales Agents and Forward Purchasers, except for Jefferies LLC and Stifel, Nicolaus & Company, Incorporated, are lenders under our revolving credit facility. To the extent that we use a portion of the net proceeds from this offering to repay outstanding Revolving Loans, such affiliates of the Sales Agents and Forward Purchasers, except for Jefferies LLC and Stifel, Nicolaus & Company, Incorporated, will receive their proportionate shares of any such amount. Stifel, Nicolaus & Company, Incorporated may pay a lender under our revolving credit facility, or such lender's affiliate, a fee in connection with this offering. Such lender is not affiliated with Stifel, Nicolaus & Company, Incorporated. In addition, affiliates of certain of the Sales Agents and Forward Purchasers have term loan commitments or are term loan lenders under the Amended Credit Agreement.

If we enter into a forward sale agreement with any Forward Purchaser, we expect that such Forward Purchaser will attempt to borrow and sell, through the relevant Sales Agent, acting as Forward Seller, shares of our common stock to hedge such Forward Purchaser's exposure under such forward sale agreement. All of the net proceeds from the sale of any such borrowed shares will be paid to the applicable Forward Purchaser (or one or more of its affiliates). Each Forward Purchaser will be either a Sales Agent or an affiliate of a Sales Agent. As a result, a Sales Agent or its affiliate will receive the net proceeds from any sale of borrowed shares of our common stock made in connection with any forward sale agreements.

In connection with the sale of common stock on our behalf, each Sales Agent and Forward Purchaser may be deemed to be an "underwriter" within the meaning of the Securities Act and compensation of the Sales Agents and Forward Purchasers may be deemed to be underwriting discounts or commissions. We have agreed to indemnify the several Sales Agents (whether acting as our sales agent, principal or Forward Seller) and Forward Purchasers against certain liabilities in connection with this offering, including liabilities under the Securities Act, or to contribute to payments such Sales Agents and Forward Purchasers may be required to make because of any of those liabilities.

Other than in the United States, no action has been taken by us, the Sales Agents or the Forward Purchasers that would permit a public offering of the securities offered by this prospectus supplement and the accompanying prospectus in any jurisdiction where action for that purpose is required. The securities offered by this prospectus supplement and the accompanying prospectus may not be offered or sold, directly or indirectly, nor may this prospectus supplement and the accompanying prospectus or any other offering material or advertisements in connection with the offer and sale of any such securities be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus supplement and the accompanying prospectus come are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution of this prospectus supplement and the accompanying prospectus. This prospectus supplement and the accompanying prospectus do not constitute an offer to sell or a solicitation of an offer to buy any securities offered by this prospectus supplement and the accompanying prospectus in any jurisdiction in which such an offer or a solicitation is unlawful.

Certain legal matters will be passed upon for us by Cravath, Swaine & Moore LLP and Skadden, Arps, Slate, Meagher & Flom LLP, and for the Sales Agents, the Forward Sellers and Forward Purchasers by Latham & Watkins LLP. Venable LLP will issue an opinion to us regarding certain matters of Maryland law, including the validity of the shares of our common stock offered hereby.

The financial statements incorporated in this prospectus supplement by reference from CyrusOne Inc.'s Annual Report on Form 10-K, as amended, for the year ended December 31, 2020, and the effectiveness of CyrusOne Inc.'s internal control over financial reporting, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports, which are incorporated herein by reference (which reports express an unqualified opinion on the financial statements and include an explanatory paragraph referring to the adoption of the FASB Accounting Standards Update 2016-02, Leases, and express an unqualified opinion on the effectiveness of internal control over financial reporting). Such financial statements have been so incorporated in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing.

CyrusOne Inc.
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CyrusOne LP
CyrusOne Finance Corp.
DEBT SECURITIES
(and guarantees thereof)

CyrusOne Inc. may, from time to time, offer and sell debt securities, common stock, preferred stock, warrants, rights and units, and certain of CyrusOne Inc.'s subsidiaries may guarantee the principal of, and premium (if any) and interest on, any such debt securities. CyrusOne LP and CyrusOne Finance Corp. may, from time to time, offer and sell debt securities, and CyrusOne Inc. and CyrusOne GP will, and certain of CyrusOne LP's subsidiaries including CyrusOne Foreign Holdings LLC, CyrusOne LLC, CyrusOne TRS Inc., Cervalis Holdings LLC, Cervalis LLC, CyrusOne-NC LLC, CyrusOne-NJ LLC, C1-Allen LLC, C1-ATL LLC, C1-Mesa LLC, C1-Sterling VIII LLC, C1-Santa Clara LLC, Warhol TRS LLC, Warhol Partnership LLC and Warhol REIT LLC may, guarantee the principal of, and premium (if any) and interest on, such debt securities.

We refer to the debt securities and the guarantees thereof, common stock, preferred stock, warrants, rights and units of CyrusOne Inc. and the debt securities of CyrusOne LP and CyrusOne Finance Corp. and the guarantees thereof registered hereunder collectively as the "securities" in this prospectus.

In addition, selling securityholders to be named in a prospectus supplement may offer and sell from time to time securities in such amounts and on such terms as set forth in such prospectus supplement. Unless otherwise set forth in a prospectus supplement, we will not receive proceeds from any sale of the securities by any selling securityholder.

To assist us in complying with certain U.S. federal income tax requirements applicable to real estate investment trusts ("REITs"), among other purposes, our charter contains certain restrictions relating to the ownership and transfer of our stock, including an ownership limit of 9.8% of our outstanding common stock and 9.8% in value of the outstanding shares of all classes and series of our stock, subject to certain exceptions. See "Restrictions on Ownership and Transfer" for a detailed description of the ownership and transfer restrictions applicable to our stock.

The specific amounts, prices and terms of each series or class of the securities will be determined at the time of any offering set forth in the applicable prospectus supplement. The applicable prospectus supplement will also contain information, where applicable, about certain federal income tax consequences relating to, and any listing on a securities exchange of, the securities covered by such prospectus supplement.

The securities may be offered directly by us or any selling securityholder, as applicable, through agents designated from time to time by us or to or through underwriters or dealers. If any agents, dealers or underwriters are involved in the sale of any of the securities, their names, and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections entitled "Plan of Distribution" and "About this Prospectus" for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such series of securities.

Our common stock is listed on NASDAQ Global Select Market under the symbol "CONE." On May 2, 2019, the last reported sale price of our common stock on the NASDAQ Global Select Market was $58.03 per share. Our principal executive offices are located at 2101 Cedar Springs Road, Suite 900, Dallas, Texas 75201 and our telephone number is (972) 350-0060.

Investing in our securities involves risk. See "Risk Factors" beginning on page 5.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Except as otherwise indicated or required by the context, references in this prospectus to (i) "CyrusOne," "we," "our," "us" and "our company" refer to CyrusOne Inc., a Maryland corporation, together with its combined subsidiaries, including CyrusOne LP, a Maryland limited partnership (our "operating partnership" or "CyrusOne LP"), and CyrusOne GP, a Maryland statutory trust of which we are the sole beneficial owner and sole trustee and which is the sole general partner of our operating partnership ("CyrusOne GP"), and (ii) "CBI" refers to Cincinnati Bell Inc., an Ohio corporation, and, unless the context otherwise requires, its consolidated subsidiaries.

You should rely only on the information contained in this prospectus, in an accompanying prospectus supplement or incorporated by reference herein or therein. We have not authorized anyone to provide you with information or make any representation that is different. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus and any accompanying prospectus supplement do not constitute an offer to sell or a solicitation of an offer to buy any securities other than the registered securities to which they relate, and this prospectus and any accompanying prospectus supplement do not constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction where, or to any person to whom, it is unlawful to make such an offer or solicitation. You should not assume that the information contained in this prospectus and any accompanying prospectus supplement is correct on any date after the respective dates of the prospectus and such prospectus supplement or supplements, as applicable, even though this prospectus and such prospectus supplement or supplements are delivered or securities are sold pursuant to the prospectus and such prospectus supplement or supplements at a later date. Since the respective dates of the prospectus contained in this registration statement and any accompanying prospectus supplement, our business, financial condition, results of operations and prospects may have changed. We may only use this prospectus to sell the securities if it is accompanied by a prospectus supplement.

This prospectus and the documents incorporated by reference herein contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the "Securities Act"), and Section 21E of the Securities Exchange Act of 1934, as amended (the "Exchange Act"). We intend such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995 and include this statement for purposes of complying with these safe harbor provisions.

In particular, statements pertaining to our capital resources, portfolio performance, financial condition and results of operations contain certain forward-looking statements. Likewise, all of our statements regarding anticipated growth in our funds from operations and anticipated market conditions, demographics and results of operations are forward-looking statements. You can identify forward-looking statements by the use of forward-looking terminology such as "believes," "expects," "may," "will," "should," "seeks," "approximately," "intends," "plans," "estimates" or "anticipates" or the negative of these words and phrases or similar words or phrases that are predictions of or indicate future events or trends and that do not relate solely to historical matters. You can also identify forward-looking statements by discussions of strategy, plans or intentions.

The following factors, among others, could cause actual results and future events to differ materially from those set forth or contemplated in the forward-looking statements:

While forward-looking statements reflect our good faith beliefs, they are not guarantees of future performance. We disclaim any obligation other than as required by law to publicly update or revise any forward-looking statement to reflect changes in underlying assumptions or factors or for new information, data or methods, future events or other changes. For a further discussion of these and other factors that could impact our future results, performance or transactions, see the section in this prospectus entitled "Risk Factors," including the risks incorporated therein from our most recent Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission ("SEC") on February 22, 2019 and our most recent Quarterly Report filed on Form 10-Q with the SEC on May 2, 2019, as updated by our subsequent filings.

This prospectus is part of a registration statement that we filed on Form S-3 with the SEC as a "well-known seasoned issuer" ("WKSI") as defined in Rule 405 under the Securities Act, using an "automatic shelf" registration process. Under this process, we or any selling securityholders may sell any combination of the securities described in this prospectus from time to time and in one or more offerings in amounts to be determined at the time of any offering. This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement containing specific information about the terms of the applicable offering. Such prospectus supplement may add, update or change information contained in this prospectus. You should read this prospectus and the applicable prospectus supplement together with additional information described under the heading "Where You Can Find More Information."

We may offer the securities directly, through agents, or to or through underwriters. The applicable prospectus supplement will describe the terms of the plan of distribution and set forth the names of any underwriters involved in the sale of the securities. See "Plan of Distribution" for more information. No securities may be sold without delivery of a prospectus supplement describing the method and terms of the offering of those securities.

We are subject to the information and reporting requirements of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), and, accordingly, file annual, quarterly and periodic reports, proxy statements and other information with the SEC.

We have filed with the SEC a registration statement on Form S-3, including exhibits and schedules filed with the registration statement of which this prospectus is a part, under the Securities Act, with respect to the securities registered hereby. This prospectus and any applicable prospectus supplement do not contain all of the information set forth in the registration statement and exhibits and schedules to the registration statement. For further information with respect to our company and the securities registered hereby, reference is made to the registration statement, including the exhibits and schedules to the registration statement. Statements contained in this prospectus and any applicable prospectus supplement as to the contents of any contract or other document referred to in this prospectus and any applicable prospectus supplement are not necessarily complete and, where that contract is an exhibit to the registration statement, each statement is qualified in all respects by the exhibit to which the reference relates.

Our SEC filings, including our registration statement, are also available to you, free of charge, on the SEC's website at www.sec.gov. Our SEC filings are also available through the "About CyrusOne—Investors—SEC Filings" tab of CyrusOne Inc.'s website at www.cyrusone.com. The information contained on or linked to or from our website is not incorporated by reference into this prospectus and should not be considered part of this prospectus or any applicable prospectus supplement.

This prospectus is part of a registration statement on Form S-3 filed with the SEC. This prospectus does not contain all of the information included in the registration statement, certain parts of which are omitted in accordance with the rules and regulations of the SEC.

The SEC allows us to "incorporate by reference" certain information into this prospectus from certain documents that we filed with the SEC prior to the date of this prospectus. By incorporating by reference, we are disclosing important information to you by referring you to documents we have filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, except for information incorporated by reference that is modified or superseded by information contained in this prospectus or in any other subsequently filed document that also is incorporated by reference herein. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to be part of this prospectus. These documents contain important information about us, our business and our finances. The following documents previously filed with the SEC are incorporated by reference into this prospectus except for any document or portion thereof deemed to be "furnished" and not filed in accordance with SEC rules:

We also incorporate by reference all documents we may file with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act on or after the date we file this prospectus, except for any document or portion thereof deemed to be "furnished" and not filed in accordance with SEC rules.

The information relating to us contained in this prospectus does not purport to be comprehensive and should be read together with the information contained in the documents incorporated or deemed to be incorporated by reference into this prospectus.

If you request, either orally or in writing, we will provide you with a copy of any or all documents that are incorporated by reference herein. Such documents will be provided to you free of charge, but will not contain any exhibits, unless those exhibits are incorporated by reference into the document. Requests can be made by writing to Investor Relations at 2101 Cedar Springs Road, Suite 900, Dallas, Texas 75201 or by telephone at (972) 350-0060. The documents may also be accessed on our website under the "About CyrusOne—Investors—SEC Filings" tab at www.cyrusone.com. Information contained on our website is not incorporated by reference into this prospectus and should not be considered part of this prospectus or any applicable prospectus supplement.

We are a fully integrated, self-managed data center real estate investment trust that owns, operates and develops enterprise-class, carrier-neutral, multi-tenant and single-tenant data center properties. Founded in 2001, CyrusOne Inc. successfully completed an initial public offering and began trading on the NASDAQ Exchange on January 18, 2013. Our data centers are generally purpose-built facilities with redundant power and cooling. They are not network specific and enable customer connectivity to a range of telecommunication carriers. We provide mission-critical data center facilities that protect and ensure the continued operation of information technology infrastructure for approximately 1,000 customers in 48 data centers and two recovery centers in 13 markets (10 cities in the U.S., London, U.K., Singapore and Frankfurt, Germany).

We have elected to be treated as a REIT for U.S. federal income tax purposes commencing with our taxable year ended December 31, 2013. Our principal executive offices are located at 2101 Cedar Springs Road, Suite 900, Dallas, TX 75201. Our telephone number is (972) 350-0060.

An investment in any securities offered by this prospectus involves risks. You should carefully consider the risk factors incorporated by reference to our most recent Annual Report on Form 10-K and most recent Quarterly Report on Form 10-Q and the other information contained in this prospectus, as updated by our subsequent filings under the Exchange Act, before purchasing any of such securities. See "Where You Can Find More Information" for information about how to obtain a copy of these documents. You should also carefully consider the risks and other information that may be contained in, or incorporated by reference into, any prospectus supplement relating to the specific offering of securities.

We may register securities covered by this prospectus for re-offers and resales by any selling securityholders to be named in a prospectus supplement. Because we are a WKSI, we may add secondary sales of securities by any selling securityholders by filing a prospectus supplement with the SEC. We may register these securities to permit securityholders to resell their securities when they deem appropriate. A selling securityholder may resell all, a portion or none of their securities at any time and from time to time. We may register those securities for sale through an underwriter or other plan of distribution as set forth in a prospectus supplement. See "Plan of Distribution." Selling securityholders may also sell, transfer or otherwise dispose of some or all of their securities in transactions exempt from the registration requirements of the Securities Act. We may pay all expenses incurred with respect to the registration of the securities owned by the selling securityholders, other than underwriting fees, discounts or commissions, which will be borne by the selling securityholders. We will provide you with a prospectus supplement naming the selling securityholders, the amount of securities to be registered and sold and other terms of the securities being sold by a selling securityholder.

Unless otherwise set forth in a prospectus supplement, we intend to directly or indirectly contribute the net proceeds from any sale of the securities, other than certain debt securities, by CyrusOne Inc. pursuant to this prospectus to our operating partnership in exchange for operating partnership units or operating partnership equivalent units. Our operating partnership will subsequently

use the net proceeds received from us, and any primary proceeds from offerings by our operating partnership, to potentially acquire or develop additional properties, to redeem outstanding operating partnership units and for general corporate purposes, which may include payment of distributions, the repayment of existing indebtedness, acquisitions and capital expenditures for improvements to the properties in our portfolio. Pending application of cash proceeds, we will invest the net proceeds in interest-bearing accounts and short-term, interest bearing securities that are consistent with our intention to continue to qualify as a REIT for federal income tax purposes. Further details regarding the use of the net proceeds of a specific series or class of the securities will be set forth in the applicable prospectus supplement. Unless otherwise set forth in a prospectus supplement, we will not receive any proceeds from any sales of our securities by any selling securityholder.

The following description of the debt securities outlines some of the provisions of the debt securities. This information may not be complete in all respects and is qualified in its entirety by reference to the applicable indenture and its associated documents, including the form of note. We have filed forms of the indentures with the SEC as exhibits to the registration statement of which this prospectus forms a part. See "Where You Can Find More Information" for information on how to obtain copies of them. The indentures will be qualified under the Trust Indenture Act of 1939. The specific terms of any series of debt securities will be described in the applicable prospectus supplement. If so described in a prospectus supplement, the terms of that series of debt securities may differ from the general description of terms presented below and the form of indenture filed as an exhibit to the registration statement of which this prospectus forms a part.

Please note that, in this section titled "Description of Debt Securities," references to "we," "our" and "us" refer either to CyrusOne Inc., or, collectively, to CyrusOne LP and CyrusOne Finance Corp., as the case may be, as the issuer or issuers, as applicable, of the applicable series of debt securities and not to any subsidiaries, unless the context requires otherwise.

The indentures do not limit the aggregate principal amount of debt securities that may be issued thereunder. The debt securities may be issued from time to time in one or more series.

We will describe in the applicable prospectus supplement the terms relating to a series of debt securities, including:

We will set forth in the prospectus supplement the terms on which a series of debt securities may be convertible into or exchangeable for CyrusOne Inc. common stock or other securities, including the conversion or exchange rate, as applicable, or how it will be calculated, and the applicable conversion or exchange period. We will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of our securities that the holders of the series of debt securities receive upon conversion or exchange would, under the circumstances described in those provisions, be subject to adjustment, or pursuant to which those holders would, under those circumstances, receive other property upon conversion or exchange, for example in the event of our merger or consolidation with another entity.

The indenture may include covenants of CyrusOne Inc., CyrusOne LP, CyrusOne Finance Corp. or any of their subsidiaries, as the case may be. These covenants may impose limitations on our indebtedness, limitations on liens, limitations on the issuance of preferred stock of certain of our subsidiaries, limitations on certain distributions and limitations on transactions with our affiliates, or

other limitations. Any such covenants applicable to a series of debt securities will be set forth in the prospectus supplement.

The indentures in the forms initially filed as exhibits to the registration statement of which this prospectus is a part do not contain any covenant that restricts the ability of CyrusOne Inc., CyrusOne LP, CyrusOne Finance Corp. or any of their subsidiaries to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of their assets. However, any successor of such entity or acquiror of such assets must assume all of the obligations of CyrusOne Inc., CyrusOne LP, CyrusOne Finance Corp. or any of their subsidiaries, as applicable, under the indentures and the debt securities.

If the debt securities are convertible into other securities of CyrusOne Inc., CyrusOne LP, CyrusOne Finance Corp. or any of their subsidiaries, as applicable, the person with whom such entity consolidates or merges or to whom such entity sells all of its property must make provisions for the conversion of the debt securities into securities similar to the debt securities which the holders of the debt securities would have received if they had converted the debt securities before the consolidation, merger or sale.

The debt securities issued by CyrusOne Inc. may be fully and unconditionally guaranteed by certain subsidiaries of CyrusOne Inc. Unless otherwise described in the applicable prospectus supplement, the debt securities issued by CyrusOne LP and CyrusOne Finance Corp. will be fully and unconditionally guaranteed by CyrusOne Inc., CyrusOne GP and certain of CyrusOne LP's subsidiaries including CyrusOne Foreign Holdings LLC, CyrusOne LLC, CyrusOne TRS Inc., Cervalis Holdings LLC, Cervalis LLC, CyrusOne-NC LLC, CyrusOne-NJ LLC, C1-Allen LLC, C1-ATL LLC, C1-Mesa LLC, C1-Sterling VIII LLC, C1-Santa Clara LLC, Warhol TRS LLC, Warhol Partnership LLC and Warhol REIT LLC. These guarantees will be joint and several obligations of the guarantors. If a series of debt securities is so guaranteed, an indenture, or a supplemental indenture thereto, will be executed by the guarantor. The obligations of each guarantor under its guarantee will be limited as necessary to prevent that guarantee from constituting a fraudulent conveyance under applicable law. The terms of the guarantee will be set forth in the applicable prospectus supplement.

Unless otherwise specified in the applicable prospectus supplement, the following are events of default under the indentures with respect to any series of debt securities that we may issue:

If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the penultimate bullet point above, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may, and the trustee at the request of the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series will, declare the unpaid principal, premium, if any, and accrued interest, if any, due and payable immediately. Upon a declaration of acceleration, such principal of, premium, if any, and accrued interest will be immediately due and payable. If an event of default specified in the penultimate bullet point above occurs with respect to us, the principal amount of and accrued interest, if any, of each series of debt securities then outstanding shall be due and payable without any notice or other action on the part of the trustee or any holder.

The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except that defaults or events of default regarding payment of principal, premium, if any, or interest, require the consent of each holder affected by such waiver.

The holders of at least a majority in principal amount of the outstanding debt securities of any series may direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee. However, the trustee may refuse to follow any direction that conflicts with law or the applicable indenture, that may involve the trustee in personal liability, or that the trustee determines in good faith may be unduly prejudicial to the rights of holders not joining in the giving of such direction and may take any other action it deems proper that is not inconsistent with any such direction received from holders of the applicable series of debt securities. A holder may not pursue any remedy with respect to the indenture or the debt securities unless:

However, such limitations do not apply to the right of any holder of a debt security to receive payment of the principal of, premium, if any, or interest on, such debt security or to bring suit for the enforcement of any such payment on or after the due date expressed in the debt security, which right shall not be impaired or affected without the consent of the holder.

We will periodically file statements with the trustee regarding our compliance with the covenants in the indentures.

Subject to certain limited exceptions, modifications, waivers and amendments of the indentures, the debt securities and the debt security guarantees may be made with the consent of the holders of not less than a majority in aggregate principal amount of the outstanding notes (including consents obtained in connection with a tender offer or exchange offer for the notes) and any past default or

compliance with any provisions may also be waived with the consent of the holders of a majority in principal amount of the outstanding notes; provided that no such modification, waiver or amendment may, without the consent of each holder affected thereby:

Modifications, waivers and amendments of the indentures, the debt securities and the debt security guarantees may, without notice to or the consent of any holder be made:

We may at any time, at the option of the applicable board of directors evidenced by a board resolution set forth in an officers' certificate, elect to have all of our obligations discharged with respect to the outstanding debt securities of any series and all obligations of any guarantors discharged with respect to their guarantees ("Legal Defeasance") except for:

In addition, we may, at our option and at any time, elect to have our obligations and the obligations of any guarantors released with respect to certain covenants to be described in the applicable indenture ("Covenant Defeasance") and thereafter any omission to comply with those covenants will not constitute a default or event of default with respect to the debt securities of the applicable series. In the event Covenant Defeasance occurs, all events of default (except those relating to payments on the debt securities of the applicable series or bankruptcy, receivership, rehabilitation or insolvency events with respect to us) will no longer constitute an event of default with respect to such debt securities.

Each indenture will be discharged and will cease to be of further effect as to all debt securities issued thereunder, when:

We will issue the debt securities of each series only in fully registered form without coupons and, unless we otherwise specify in the applicable prospectus supplement, in minimum denominations of $2,000 and any integral multiples of $1,000 in excess of $2,000. The indentures provide that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with a depositary named by us and identified in a prospectus supplement with respect to that series.

Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, the holder will be required to pay any related taxes or other governmental charges.

We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities.

If we elect to redeem the debt securities of any series, we will not be required to:

The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs. Subject to this provision, the trustee is under no obligation to exercise any of the powers given it by the indentures at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

The indentures and provisions of the Trust Indenture Act of 1939 contain limitations on the rights of the trustee, should it become a creditor of us or any guarantor, to obtain payment of claims in certain cases or to realize on certain property received by it in respect of any such claims, as security or otherwise. The trustee is permitted to engage in other transactions; provided that if it acquires any conflicting interest, it must eliminate such conflict or resign.

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

We will pay principal of, and any premium and interest on, the debt securities of a particular series at the office of the paying agents designated by us, except that, unless we otherwise indicate in the applicable prospectus supplement, we may make payments of principal or interest by check which we will mail to the holder or by wire transfer to certain holders. The trustee will initially act as paying agent and registrar. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the debt securities of a particular series.

The indentures, the debt securities and any guarantees thereunder will be governed by and construed in accordance with the laws of the State of New York.

The following summary of the terms of the common stock of our company does not purport to be complete and is subject to and qualified in its entirety by reference to the Maryland General Corporation Law (the "MGCL") and our charter and bylaws. Copies of our charter and bylaws have been filed with the SEC and are incorporated by reference as exhibits to the registration statement of which this prospectus is a part. See "Where You Can Find More Information."

Our charter provides that we may issue up to 500,000,000 shares of common stock, $0.01 par value per share. Our charter authorizes our board of directors, without stockholder approval, to amend our charter to increase or decrease the aggregate number of shares of stock that we are authorized to issue or the number of authorized shares of any class or series of stock.

As of April 25, 2019, there were 113,172,973 shares of our common stock issued and outstanding. Under Maryland law, our stockholders generally are not liable for our debts or obligations solely as a result of their status as stockholders.

All shares of our common stock offered hereby will be duly authorized, fully paid and nonassessable. Subject to the preferential rights, if any, of holders of any other class or series of our stock and to the provisions of our charter relating to the restrictions on ownership and transfer of our stock, holders of our common stock are entitled to receive distributions when authorized by our board of directors and declared by us out of assets legally available for distribution to our stockholders and are entitled to share ratably in our assets legally available for distribution to our stockholders in the event of our liquidation, dissolution or winding up after payment of or adequate provision for all of our known debts and liabilities.

Subject to the provisions of our charter regarding the restrictions on ownership and transfer of our stock and except as may be otherwise specified in the terms of any class or series of common stock, each outstanding share of common stock entitles the holder to one vote on all matters submitted to a vote of stockholders, including the election of directors, and, except as may be provided with respect to any other class or series of our stock, the holders of shares of our common stock possess the exclusive voting power. There is no cumulative voting in the election of directors. Consequently, the holders of a majority of the outstanding shares of our common stock can elect all of the directors then standing for election, and the holders of the remaining shares will not be able to elect any directors. Directors are elected by a plurality of all of the votes cast in the election of directors.

Holders of shares of our common stock have no preference, conversion, exchange, sinking fund, redemption or appraisal rights and have no preemptive rights to subscribe for any securities of our company. Subject to the provisions of our charter regarding the restrictions on ownership and transfer of our stock, shares of our common stock have equal distribution, liquidation and other rights.

Under the MGCL, a Maryland corporation generally cannot dissolve, amend its charter, merge or consolidate with, or convert to, another entity, sell all or substantially all of its assets or engage in a statutory share exchange unless the action is advised by the board of directors and approved by the affirmative vote of stockholders entitled to cast at least two-thirds of the votes entitled to be cast on the matter, unless a lesser percentage (but not less than a majority of all of the votes entitled to be cast on the matter) is specified in the corporation's charter. Our charter provides that these actions must be approved by a majority of all of the votes entitled to be cast on the matter.

Maryland law also permits a corporation to transfer all or substantially all of its assets without the approval of its stockholders to an entity owned, directly or indirectly, by the corporation. Because our operating assets are held by our operating partnership's subsidiaries, these subsidiaries may be able to merge or transfer all or substantially all of their assets without the approval of our stockholders.

Power to Increase or Decrease Authorized Shares of Common Stock, Reclassify Unissued Shares of Common Stock and Issue Additional Shares of Common Stock

Our charter authorizes our board of directors, with the approval of a majority of the entire board and without stockholder approval, to amend our charter to increase or decrease the aggregate number of shares of stock or the number of shares of any class or series of stock that we are authorized to issue. In addition, our charter authorizes our board of directors to authorize the issuance from time to time of shares of our common stock.

Our charter also authorizes our board of directors to classify and reclassify any unissued shares of our common stock into other classes or series of stock, including one or more classes or series of stock that have priority over our common stock with respect to voting rights, distributions or upon liquidation, and authorize us to issue the newly classified shares. Prior to the issuance of shares of each new class or series of stock, our board of directors is required by Maryland law and by our charter to set, subject to the provisions of our charter regarding the restrictions on ownership and transfer of our stock, the preferences, conversion and other rights, voting powers, restrictions, limitations as to distributions, qualifications and terms and conditions of redemption for each class or series. Therefore, although our board of directors does not currently intend to do so, it could authorize the issuance of shares of common stock with terms and conditions that could have the effect of delaying, deferring or preventing a change in control or other transaction that might involve a premium price for shares of our common stock or otherwise be in the best interests of our stockholders.

We believe that the power of our board of directors to approve amendments to our charter to increase or decrease the number of authorized shares of stock, to authorize us to issue additional authorized but unissued shares of common stock and to classify or reclassify unissued shares of common stock and thereafter to authorize us to issue such classified or reclassified shares of stock provides us with increased flexibility in structuring possible future financings and acquisitions and in meeting other needs that might arise.

The transfer agent and registrar for our common stock is Computershare Trust Company N.A.

Our common stock is listed on the NASDAQ Global Select Market under the symbol "CONE."

The following summary of the terms of the preferred stock of our company does not purport to be complete and is subject to and qualified in its entirety by reference to the MGCL and our charter and bylaws. Copies of our charter and bylaws have been filed with the SEC and are incorporated by reference as exhibits to the registration statement of which this prospectus is a part. See "Where You Can Find More Information." When we offer to sell a particular class or series of stock, we will describe the specific terms of the series in a prospectus supplement. Accordingly, for a description of the terms of any class or series of stock, you must refer to both the prospectus supplement relating to that class or series and the description of stock in this prospectus. To the extent the information contained in the prospectus supplement differs from this summary description, you should rely on the information in the prospectus supplement.

Our charter provides that we may issue up to 100,000,000 shares of preferred stock, par value $0.01 per share. Our charter authorizes our board of directors, without stockholder approval, to amend our charter to increase or decrease the aggregate number of shares of stock that we are authorized to issue or the number of authorized shares of any class or series of stock. As of April 25, 2019, there were no shares of our preferred stock issued and outstanding. Under Maryland law, our stockholders generally are not liable for our debts or obligations solely as a result of their status as stockholders.

All shares of our preferred stock offered hereby will be duly authorized, fully paid and nonassessable. The specific terms of a particular class or series of preferred stock will be described in the prospectus supplement relating to that class or series, including a prospectus supplement providing that preferred stock may be issuable upon the exercise of warrants we issue. The description of preferred stock set forth below and the description of the terms of a particular class or series of preferred stock set forth in the applicable prospectus supplement do not purport to be complete and are qualified in their entirety by reference to the articles supplementary relating to that class or series.

The preferences and other terms of the preferred stock of each class or series will be fixed by the articles supplementary relating to such class or series. A prospectus supplement, relating to each class or series, will specify the terms of the preferred stock as follows:

Unless otherwise specified in the applicable prospectus supplement, the preferred stock will, with respect to dividend rights and rights upon liquidation, dissolution or winding up of our company, rank: (1) senior to all classes or series of our common stock, and to any other class or series of our stock expressly designated as ranking junior to the preferred stock; (2) on parity with any class or series of our stock expressly designated as ranking on parity with the preferred stock; and (3) junior to any other class or series of our stock expressly designated as ranking senior to the preferred stock.

The terms and conditions, if any, upon which any shares of any class or series of preferred stock are convertible into our common stock will be set forth in the applicable prospectus supplement relating thereto. Such terms will include the number of shares of our common stock into which the shares of preferred stock are convertible, the conversion price (or manner of calculation thereof), the conversion period, provisions as to whether conversion will be at the option of the holders of such class or series of preferred stock, the events requiring an adjustment of the conversion price and provisions affecting conversion in the event of the redemption of such class or series of preferred stock.

Power to Increase or Decrease Authorized Shares of Preferred Stock, Reclassify Unissued Shares of Preferred Stock and Issue Additional Shares of Preferred Stock

Our charter also authorizes our board of directors to classify and reclassify any unissued shares of our preferred stock into other classes or series of stock, including one or more classes or series of stock that have priority over our common stock with respect to voting rights, distributions or upon liquidation, and authorize us to issue the newly classified shares. Prior to the issuance of shares of each new class or series, our board of directors is required by Maryland law and by our charter to set, subject to the provisions of our charter regarding the restrictions on ownership and transfer of our stock, the preferences, conversion and other rights, voting powers, restrictions, limitations as to distributions, qualifications and terms and conditions of redemption for each class or series. Therefore, although our board of directors does not currently intend to do so, it could authorize the issuance of shares of preferred stock with terms and conditions that could have the effect of delaying, deferring or preventing a change in control or other transaction that might involve a premium price for shares of our common stock or otherwise be in the best interests of our stockholders. No shares of preferred stock are presently outstanding, and we have no present plans to issue any shares of preferred stock.

We believe that the power of our board of directors to approve amendments to our charter to increase or decrease the number of authorized shares of stock, to authorize us to issue additional authorized but unissued shares of preferred stock and to classify or reclassify unissued shares of preferred stock and thereafter to authorize us to issue such classified or reclassified shares of stock provides us with increased flexibility in structuring possible future financings and acquisitions and in meeting other needs that might arise.

To assist us in complying with certain U.S. federal income tax requirements applicable to REITs, among other purposes, our charter contains certain restrictions relating to the ownership and transfer of our stock, including an ownership limit of 9.8% in value of the aggregate of the outstanding shares of all classes or series of our stock, subject to certain exceptions. Our board may, from time to time, grant waivers from these restrictions, in its sole discretion. See "Restrictions on Ownership and Transfer" on page 26. We may choose to adopt similar restrictions with respect to any class or series offered pursuant to this prospectus under the articles supplementary for each such class or series. The applicable prospectus supplement will specify any additional ownership limitation relating to such class or series.

We may issue warrants for the purchase of debt securities, common stock or preferred stock and may issue warrants independently or together with debt securities, common stock or preferred stock or attached to or separate from such securities. We will issue each series of warrants under a separate warrant agreement between us and a bank or trust company as warrant agent, as specified in the applicable prospectus supplement. To the extent the information contained in the prospectus supplement differs from this summary description, you should rely on the information in the prospectus supplement. The warrant agent will act solely as our agent in connection with the warrants and will not act for or on behalf of warrant holders. The following sets forth certain general terms and provisions of the warrants that may be offered under this registration statement, and is qualified in its entirety by reference to the relevant warrant agreement with respect to warrants of a particular series. Further terms of the warrants and the applicable warrant agreement will be set forth in the applicable prospectus supplement.

The applicable prospectus supplement will describe the terms of the debt warrants in respect of which this prospectus is being delivered, including, where applicable, the following:

Debt warrant certificates will be exchangeable for new debt warrant certificates of different denominations and debt warrants may be exercised at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement. Prior to the exercise of their debt warrants, holders of debt warrants will not have any of the rights of holders of the securities purchasable upon such exercise, and will not be entitled to payments of principal, premium or interest on, the securities purchasable upon the exercise of debt warrants.

The applicable prospectus supplement will describe the terms of the warrants to purchase common stock or preferred stock ("equity warrants"), in respect of which this prospectus is being delivered, including, where applicable, the following:

Equity warrant certificates will be exchangeable for new equity warrant certificates of different denominations and warrants may be exercised at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement. Prior to the exercise of their equity warrants, holders of equity warrants will not have any of the rights of holders of the securities purchasable upon such exercise or to any dividend payments or voting rights as to which holders of the common stock or preferred stock purchasable upon such exercise may be entitled.

Except as provided in the applicable prospectus supplement, the exercise price and the number of shares of common stock or shares of preferred stock purchasable upon the exercise of each equity warrant will be subject to adjustment in certain events, including the issuance of a stock dividend to the holders of the underlying common stock or preferred stock or a stock split, reverse stock split, combination, subdivision or reclassification of the underlying common stock or preferred stock, as the case may be. In lieu of adjusting the number of shares purchasable upon exercise of each equity warrant, we may elect to adjust the number of equity warrants. Unless otherwise provided in the applicable prospectus supplement, no adjustments in the number of shares purchasable upon exercise of the equity warrants will be required until all cumulative adjustments require an adjustment of at least 1% thereof. We may, at our option, reduce the exercise price at any time. No fractional shares will be issued upon exercise of equity warrants, but we will pay the cash value of any fractional shares otherwise issuable.

Notwithstanding the foregoing, except as otherwise provided in the applicable prospectus supplement, in case of any consolidation, merger or sale or conveyance of our property as an entirety or substantially as an entirety, the holder of each outstanding equity warrant will have the right to the kind and amount of shares of stock and other securities and property, including cash, receivable by a holder of the number of shares of common stock or shares of preferred stock into which each equity warrant was exercisable immediately prior to the particular triggering event.

To assist us in complying with certain U.S. federal income tax requirements applicable to REITs, among other purposes, our charter contains certain restrictions relating to the ownership and transfer of our stock, including an ownership limit of 9.8% of our outstanding common stock and 9.8% in value of the outstanding shares of all classes or series of our stock, subject to certain exceptions. Our board may, from time to time, grant waivers from these restrictions, in its sole discretion. See "Restrictions on Ownership and Transfer" on page 26. We may choose to adopt similar restrictions with respect to any series or class of stock underlying the equity warrants offered pursuant to this prospectus under the articles supplementary or other charter document, as applicable, for each such class or series of stock. The applicable prospectus supplement will specify any additional ownership limitation relating to such equity warrants or class or series of stock underlying the equity warrants.

Each warrant will entitle the holder to purchase for cash such number of debt securities, shares of common stock or shares of preferred stock, at such exercise price as shall, in each case, be set forth in, or be determinable as set forth in, the applicable prospectus supplement relating to the warrants offered thereby. Unless otherwise specified in the applicable prospectus supplement, warrants may be exercised at any time up to 5:00 p.m. New York City time on the expiration date set forth in applicable prospectus supplement. After 5:00 p.m. New York City time on the expiration date, unexercised warrants will be void.

Warrants may be exercised as set forth in the applicable prospectus supplement relating to the warrants. Upon receipt of payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will, as soon as practicable, forward the securities purchasable upon such exercise. If less than all of the warrants that are represented by such warrant certificate are exercised, a new warrant certificate will be issued for the remaining amount of warrants.

We may issue rights to our stockholders to purchase debt securities, common stock, or preferred stock. Each series of rights will be issued under a separate rights agreement to be entered into between us and a bank or trust company, as rights agent, as specified in the applicable prospectus supplement. The rights agent will act solely as our agent in connection with the certificates relating to the rights of the series of certificates and will not assume any obligation or relationship of agency or trust for or with any holders of rights certificates or beneficial owners of rights. The following sets forth certain general terms and provisions of the rights that may be offered under this registration statement, and is qualified in its entirety by reference to the relevant rights agreement with respect to rights of a particular series. Further terms of the rights and the applicable rights agreement will be set forth in the applicable prospectus supplement. To the extent the information contained in the prospectus supplement differs from this summary description, you should rely on the information in the prospectus supplement.

We will provide in a prospectus supplement the following terms of the rights being issued:

Each right will entitle the holder of rights to purchase for cash the principal amount of debt securities, shares of common stock or shares of preferred stock at the exercise price provided in the applicable prospectus supplement. Rights may be exercised at any time up to the close of business on the expiration date for the rights provided in the applicable prospectus supplement. After the close of business on the expiration date, all unexercised rights will be void.

Holders may exercise rights as described in the applicable prospectus supplement. Upon receipt of payment and the rights certificate properly completed and duly executed at the corporate trust office of the rights agent or any other office indicated in the prospectus supplement, we will, as soon as practicable, forward the debt securities, shares of common stock or shares of preferred stock purchasable upon exercise of the rights. If less than all of the rights issued in any rights offering are exercised, we may offer any unsubscribed securities directly to persons other than securityholders, to or through agents, underwriters or dealers or through a combination of such methods, including pursuant to standby underwriting arrangements, as described in the applicable prospectus supplement.

We may issue units consisting of two or more other constituent securities. These units may be issuable as, and for a specified period of time may be transferable only as, a single security, rather than as the separate constituent securities comprising such units. The following sets forth certain general terms and provisions of the units that may be offered under this registration statement. Further terms of the units will be set forth in the applicable prospectus supplement. To the extent the information contained in the prospectus supplement differs from this summary description, you should rely on the information in the prospectus supplement.

When we issue units, we will provide in a prospectus supplement the following terms of the units being issued:

The following summary with respect to restrictions on ownership and transfer of our stock (including warrants and rights to acquire our stock) sets forth certain general terms and provisions of our charter to which any prospectus supplement may relate. For purposes of this summary, references to "tenants" mean those persons who are referred to as "customers" elsewhere in this prospectus. This summary does not purport to be complete and is subject to and qualified in its entirety by reference to our charter, including any articles supplementary relating to any issuance of preferred stock pursuant to this prospectus. A copy of our charter has been filed with the SEC and is incorporated by reference as an exhibit to the registration statement of which this prospectus is a part. Any amendment or supplement to our charter relating to an issuance of securities pursuant to this prospectus shall be filed with the SEC and shall be filed or incorporated by reference as an exhibit to the applicable prospectus supplement. See "Where You Can Find More Information."

In order for us to qualify as a REIT under the Code, shares of our stock must be owned by 100 or more persons during at least 335 days of a taxable year of 12 months (other than the first year for which an election to qualify as a REIT has been made) or during a proportionate part of a shorter taxable year. Also, not more than 50% of the value of the outstanding shares of our stock may be owned, directly or indirectly, by five or fewer individuals (as defined in the Code to include certain entities such as private foundations) during the last half of a taxable year (other than the first year for which an election to be a REIT has been made). To qualify as a REIT, we must satisfy other requirements as well. See "U.S. Federal Income Tax Considerations—Requirements for Qualification—General."

Our charter contains restrictions on the ownership and transfer of our stock. Our board may, from time to time, grant waivers from these restrictions, in its sole discretion. The relevant sections of our charter provide that, subject to the exceptions described below, no person or entity may own, or be deemed to own, beneficially or by virtue of the applicable constructive ownership provisions of the Code, more than 9.8%, in value or in number of shares, whichever is more restrictive, of the outstanding shares of our common stock (the "common stock ownership limit") or 9.8% in value of the outstanding shares of all classes or series of our stock (the "aggregate stock ownership limit"). We refer to the common stock ownership limit and the aggregate stock ownership limit collectively as the "ownership limits." We refer to the person or entity that, but for operation of the ownership limits or another restriction on ownership and transfer of our stock as described below, would beneficially own or constructively own shares of our stock in violation of such limits or restrictions and, if appropriate in the context, a person or entity that would have been the record owner of such shares of our stock as a "prohibited owner."

The constructive ownership rules under the Code are complex and may cause shares of stock owned beneficially or constructively by a group of related individuals and/or entities to be owned beneficially or constructively by one individual or entity. As a result, the acquisition of less than 9.8%, in value or in number of shares, whichever is more restrictive, of the outstanding shares of our common stock, or less than 9.8% in value of the outstanding shares of all classes and series of our stock (or the acquisition by an individual or entity of an interest in an entity that owns, beneficially or constructively, shares of our stock), could, nevertheless, cause that individual or entity, or another individual or entity, to own beneficially or constructively shares of our stock in excess of the ownership limits.

Our board of directors, in its sole discretion, may exempt, prospectively or retroactively, a particular stockholder from the ownership limits or establish a different limit on ownership (the "excepted holder limit") if our board of directors determines that:

Any violation or attempted violation of any such representations or undertakings will result in such stockholder's shares of stock being automatically transferred to a charitable trust. As a condition of granting the waiver or establishing the excepted holder limit, our board of directors may require an opinion of counsel or a ruling from the IRS, in either case in form and substance satisfactory to our board of directors, in its sole discretion, in order to determine or ensure our status as a REIT and such representations and undertakings from the person requesting the exception as our board of directors may require in its sole discretion to make the determinations above. Our board of directors may impose such conditions or restrictions as it deems appropriate in connection with granting such a waiver or establishing an excepted holder limit. As of the date hereof, our board has granted limited waivers to certain holders of our common stock.

In connection with granting a waiver of the ownership limits or creating an excepted holder limit or at any other time, our board of directors may from time to time increase or decrease the common stock ownership limit, the aggregate stock ownership limit or both, for all other persons, unless, after giving effect to such increase, five or fewer individuals could beneficially own, in the aggregate, more than 49.9% in value of our outstanding stock or we would otherwise fail to qualify as a REIT. A reduced ownership limit will not apply to any person or entity whose percentage ownership of our common stock or our stock of all classes and series, as applicable, is, at the effective time of such reduction, in excess of such decreased ownership limit until such time as such person's or entity's percentage ownership of our common stock or our stock of all classes and series, as applicable, equals or falls below the decreased ownership limit, but any further acquisition of shares of our common stock or stock of all other classes or series, as applicable, will violate the decreased ownership limit.

Any person who acquires or attempts or intends to acquire beneficial or constructive ownership of shares of our stock that will or may violate the ownership limits or any of the other restrictions on ownership and transfer of our stock described above, or who would have owned shares of our stock

transferred to the trust as described below, must immediately give notice to us of such event or, in the case of an attempted or proposed transaction, give us at least 15 days' prior written notice and provide us with such other information as we may request in order to determine the effect of such transfer on our status as a REIT.

If any transfer of shares of our stock would result in shares of our stock being beneficially owned by fewer than 100 persons, the transfer will be null and void and the intended transferee will acquire no rights in the shares. In addition, if any purported transfer of shares of our stock or any other event would otherwise result in any person violating the ownership limits or an excepted holder limit established by our board of directors, or in our being "closely held" under Section 856(h) of the Code (without regard to whether the ownership interest is held during the last half of a taxable year) or otherwise failing to qualify as a REIT or as a "domestically controlled qualified investment entity" within the meaning of Section 897(h) of the Code, then that number of shares (rounded up to the nearest whole share) that would cause the violation will be automatically transferred to, and held by, a trust for the exclusive benefit of one or more charitable organizations selected by us, and the intended transferee or other prohibited owner will acquire no rights in the shares. The automatic transfer will be effective as of the close of business on the business day prior to the date of the violative transfer or other event that results in a transfer to the trust. If the transfer to the trust as described above is not automatically effective, for any reason, to prevent violation of the applicable ownership limits or our being "closely held" under Section 856(h) of the Code (without regard to whether the ownership interest is held during the last half of a taxable year) or our otherwise failing to qualify as a REIT or as a "domestically controlled qualified investment entity," then our charter provides that the transfer of the shares will be null and void and the intended transferee will acquire no rights in such shares.

Shares of our stock held in the trust will be issued and outstanding shares. The prohibited owner will not benefit economically from ownership of any shares of our stock held in the trust and will have no rights to distributions and no rights to vote or other rights attributable to the shares of our stock held in the trust. The trustee of the trust will exercise all voting rights and receive all distributions with respect to shares held in the trust for the exclusive benefit of the charitable beneficiary of the trust. Any distribution made before we discover that the shares have been transferred to a trust as described above must be repaid by the recipient to the trustee upon demand by us. Subject to Maryland law, effective as of the date that the shares have been transferred to the trust, the trustee will have the authority to rescind as void any vote cast by a prohibited owner before our discovery that the shares have been transferred to the trust and to recast the vote in accordance with the desires of the trustee acting for the benefit of the charitable beneficiary of the trust. However, if we have already taken irreversible corporate action, then the trustee may not rescind and recast the vote.

Shares of our stock transferred to the trustee are deemed offered for sale to us, or our designee, at a price per share equal to the lesser of (i) the price paid by the prohibited owner for the shares (or, in the case of a devise or gift, the market price at the time of such devise or gift) and (ii) the market price on the date we accept, or our designee, accepts such offer. We may reduce the amount so payable to the trustee by the amount of any distribution that we made to the prohibited owner before we discovered that the shares had been automatically transferred to the trust and that are then owed by the prohibited owner to the trustee as described above, and we may pay the amount of any such reduction to the trustee for distribution to the charitable beneficiary. We have the right to accept such offer until the trustee has sold the shares of our stock held in the trust as discussed below. Upon a sale to us, the interest of the charitable beneficiary in the shares sold terminates, and the trustee must distribute the net proceeds of the sale to the prohibited owner and must distribute any distributions held by the trustee with respect to such shares to the charitable beneficiary.

If we do not buy the shares, the trustee must, within 20 days of receiving notice from us of the transfer of shares to the trust, sell the shares to a person or entity designated by the trustee who could own the shares without violating the ownership limits or the other restrictions on ownership and

transfer of our stock. After the sale of the shares, the interest of the charitable beneficiary in the shares transferred to the trust will terminate and the trustee must distribute to the prohibited owner an amount equal to the lesser of (i) the price paid by the prohibited owner for the shares (or, if the prohibited owner did not give value for the shares in connection with the event causing the shares to be held in the trust (for example, in the case of a gift, devise or other such transaction), the market price of the shares on the day of the event causing the shares to be held in the trust) and (ii) the sales proceeds (net of any commissions and other expenses of sale) received by the trust for the shares. The trustee may reduce the amount payable to the prohibited owner by the amount of any distribution that we paid to the prohibited owner before we discovered that the shares had been automatically transferred to the trust and that are then owed by the prohibited owner to the trustee as described above. Any net sales proceeds in excess of the amount payable to the prohibited owner must be paid immediately to the charitable beneficiary, together with any distributions thereon. In addition, if, prior to the discovery by us that shares of stock have been transferred to a trust, such shares of stock are sold by a prohibited owner, then such shares will be deemed to have been sold on behalf of the trust and, to the extent that the prohibited owner received an amount for or in respect of such shares that exceeds the amount that such prohibited owner was entitled to receive, such excess amount will be paid to the trustee upon demand. The prohibited owner has no rights in the shares held by the trustee.

In addition, if our board of directors determines in good faith that a transfer or other event has occurred that would violate the restrictions on ownership and transfer of our stock described above, our board of directors may take such action as it deems advisable to refuse to give effect to or to prevent such transfer, including, but not limited to, causing us to redeem shares of our stock, refusing to give effect to the transfer on our books or instituting proceedings to enjoin the transfer.

Every owner of 5% or more (or such lower percentage as required by the Code or the regulations promulgated thereunder) of our stock, within 30 days after the end of each taxable year, must give us written notice stating the stockholder's name and address, the number of shares of each class and series of our stock that the stockholder beneficially owns and a description of the manner in which the shares are held. Each such owner must provide to us in writing such additional information as we may request in order to determine the effect, if any, of the stockholder's beneficial ownership on our status as a REIT and to ensure compliance with the ownership limits. In addition, any person or entity that is a beneficial owner or constructive owner of shares of our stock and any person or entity (including the stockholder of record) who is holding shares of our stock for a beneficial owner or constructive owner must, on request, provide to us such information as we may request in good faith in order to determine our status as a REIT and to comply with the requirements of any taxing authority or governmental authority or to determine such compliance and to ensure compliance with the ownership limits.

Any certificates representing shares of our stock will bear a legend referring to the restrictions on ownership and transfer of our stock described above.

These restrictions on ownership and transfer of our stock will not apply if our board of directors determines that it is no longer in our best interests to attempt to qualify, or to continue to qualify, as a REIT or that compliance is no longer required in order for us to qualify as a REIT.

The restrictions on ownership and transfer of our stock described above could delay, defer or prevent a transaction or a change in control that might involve a premium price for our common stock or otherwise be in the best interests of our stockholders.

We have summarized the material terms and provisions of the Amended and Restated Agreement of Limited Partnership of CyrusOne LP, as amended, which we refer to as the "partnership agreement." This summary is not complete. For more detail, you should refer to the partnership agreement itself, a copy of which has been filed with the SEC and is incorporated by reference as an exhibit to the registration statement of which this prospectus is a part. For purposes of this section, references to "we," "our," "us" and "our company" refer to CyrusOne Inc.

Our operating partnership, CyrusOne LP, is a Maryland limited partnership that was formed on July 31, 2012. CyrusOne GP, our wholly-owned subsidiary, is the sole general partner of our operating partnership, and we continue to conduct substantially all of our business in or through our operating partnership. In connection with our initial public offering in January 2013, we entered into the amended and restated agreement of limited partnership, as special limited partner, with CBI and the other limited partners named therein. As of the date hereof, CBI and its subsidiaries are no longer limited partners of our operating partnership and CyrusOne Inc. and CyrusOne GP are the only partners of our operating partnership.

As the sole trustee of the sole general partner of our operating partnership, we exercise exclusive and complete responsibility and discretion in its day-to-day management and control. We can cause our operating partnership to enter into major transactions, including acquisitions, dispositions and refinancings, subject to certain limited exceptions. The limited partners of our operating partnership may not transact business for, or participate in the management activities or decisions of, our operating partnership, except as provided in the partnership agreement and as required by applicable law. The general partner of our operating partnership may not be removed as general partner by the limited partners. The partnership agreement restricts our ability to engage in certain business combinations as more fully described below.

The limited partners of our operating partnership expressly agree that the general partner of our operating partnership is acting for the benefit of our operating partnership, the limited partners of our operating partnership and our stockholders collectively. The general partner is under no obligation to give priority to the separate interests of the limited partners in deciding whether to cause our operating partnership to take or decline to take any actions. If there is a conflict between the interests of us or our stockholders, on the one hand, and the limited partners of our operating partnership, on the other, the partnership agreement provides that any action or failure to act by the general partner that gives priority to the separate interests of our stockholders or us that does not result in a violation of the contractual rights of the limited partners of our operating partnership under the partnership agreement will not violate any duty that we or the general partner owe to our operating partnership and its partners.

The partnership agreement provides that all of our business activities, including all activities pertaining to the acquisition and operation of properties, must generally be conducted through our operating partnership. The partnership agreement does permit us, under certain circumstances, to hold certain assets other than through our operating partnership. However, we must make commercially reasonable efforts to insure that the economic benefits and burdens of such assets are vested in our operating partnership.

The general partner may not transfer or assign all or any portion of its interest in our operating partnership (other than a transfer to us or one of our wholly-owned subsidiaries or in connection with a permitted Termination Transaction (as defined below)) without the consent of the partners (including

us, the general partner and entities controlled by us or the general partner) holding a majority of our operating partnership units then held by partners (including us, the general partner and entities controlled by us or the general partner) entitled to vote on or consent to such matter. The general partner may not voluntarily withdraw from our operating partnership, except in connection with a transfer of all of its interest in our operating partnership in accordance with the partnership agreement, without the consent of the limited partners (other than us, the general partner and entities controlled by us or the general partner, if there are any other limited partners) holding a majority of all the outstanding operating partnership units held by all partners (other than us, the general partner and entities controlled by us or the general partner, if there are any other limited partners) entitled to vote on or consent to such matter. A limited partner may not sell, assign, encumber or otherwise dispose of its operating partnership units in our operating partnership without the general partner's consent during the 12-month period following such limited partner's acquisition of such operating partnership units, other than to family members or trusts for their exclusive benefit, to a charity or trust for the benefit of a charity or to entities that are controlled by the limited partner, its family members or affiliates. After the 12-month period following such limited partner's acquisition of operating partnership units, any transfer of such operating partnership units by the limited partner, except to the parties specified above, will be subject to a right of first refusal by us. All transfers must be made only to "accredited investors" as defined under Rule 501 of the Securities Act and are subject to other limitations and conditions set forth in the partnership agreement.

Amendments to the partnership agreement may be proposed by the general partner, and the general partner must approve all amendments to the partnership agreement.

Generally, the partnership agreement may not be amended, modified or terminated without the approval of both the general partner and the partners holding a majority of our operating partnership units then held by all partners (including us, the general partner and entities controlled by us or the general partner) entitled to vote on, or consent to such matter. The general partner has the power to unilaterally make certain amendments to the partnership agreement without obtaining the consent of any other partners as may be required to:

Subject to certain exceptions, amendments that would, among other things, convert a limited partner into a general partner (except in connection with a permitted transfer of the general partner's interest), modify the limited liability of a limited partner, adversely alter a partner's right to receive any distributions or allocations of profits or losses, adversely alter or modify the redemption rights of limited partners and qualifying assignees (except as permitted in connection with a permitted Termination Transaction) or amend these restrictions must be approved by each limited partner that would be adversely affected by such amendment; provided, however, that the consent of any individual partner adversely affected will not be required for any amendment or action that affects all partners holding the same class or series of our operating partnership units on a uniform or pro rata basis, if approved by a majority of the partners (other than us, the general partner and entities controlled by us or the general partner, if there are any other limited partners) of such class or series.

The general partner may not take any action in contravention of an express prohibition or limitation contained in the partnership agreement, including:

In addition, without the consent of partners (including us, the general partner and entities controlled by us or the general partner) holding a majority of our operating partnership units then held by the partners (including us, the general partner and entities controlled by us or the general partner), entitled to vote on or consent to such matter, the general partner may not do any of the following:

The partnership agreement provides that holders of operating partnership units are generally entitled to receive distributions when, as and if authorized by the general partner, on a pro rata basis in accordance with their respective operating partnership units (subject to the rights of the holders of any class of preferred partnership interests that may be authorized and issued in the future).

A limited partner or an assignee has the right, commencing on or after the date which is 12 months after its acquisition of operating partnership units, to require our operating partnership to redeem part or all of such operating partnership units for cash based upon the fair market value of an equivalent number of shares of our common stock at the time of the redemption, determined in accordance with and subject to adjustment as provided in the partnership agreement. Alternatively, we may elect to acquire those operating partnership units in exchange for shares of our common stock. Our acquisition will be on a one-for-one basis, subject to adjustment in the event of stock splits, stock dividends, distributions of warrants or stock rights, specified extraordinary distributions and similar events. A limited partner or assignee may not require us to redeem such limited partner's or assignee's operating partnership units if our election to acquire such operating partnership units in exchange for shares of our common stock would cause any person to violate the ownership limits or the other restrictions on ownership and transfer of our common stock, after giving effect to any waivers or modifications of such limits granted by our board of directors. With each redemption or exchange, we increase our percentage ownership interest in our operating partnership.

In addition, if our election to acquire operating partnership units tendered for redemption in exchange for shares of our common stock would cause any person to violate the restrictions on ownership and transfer of our stock and such excess operating partnership units (and any other operating partnership units that the tendering limited partner agrees to treat as such) have a value of at least $50,000,000 (based on an operating partnership unit having a value equal to the trailing ten-day daily trading price of our common stock) and we are eligible to file a registration statement on Form S-3 under the Securities Act, then we may also elect to redeem our operating partnership units with the proceeds from a public offering or private placement of our common stock. In the event we elect this option, we may require the other limited partners to also elect whether or not to participate. Participating limited partners will receive on the redemption date for each operating partnership unit (subject to adjustment) the net proceeds per share received in the public offering but will have a limited opportunity to withdraw their operating partnership units from the redemption immediately prior to the pricing of the public offering.

The general partner of our operating partnership has the power to cause our operating partnership to issue additional units of partnership interest in one or more classes or series. These additional units of partnership interest may include preferred partnership units or LTIP units. Generally, we may issue additional shares of our stock, or rights, options, warrants or convertible or exchangeable securities

having the right to subscribe for or purchase shares of our stock, only if we cause our operating partnership to issue to us (or the general partner) partnership interests or rights, options, warrants or convertible or exchangeable securities of our operating partnership having economic rights that are substantially similar to the securities that we have issued.

The partnership agreement provides that the general partner may authorize the issuance of additional partnership interests in exchange for such capital contributions, if any, as the general partner may approve. Under the partnership agreement, we are generally obligated to contribute the net proceeds we receive from any offering of our shares of stock as additional capital to our operating partnership in exchange for additional operating partnership units issued to us or the general partner.

The partnership agreement provides that we or the general partner may make additional capital contributions, including contributions of properties, to our operating partnership in exchange for additional operating partnership units. If we contribute (directly or indirectly through the general partner) additional capital and receive additional operating partnership units in exchange for the capital contribution, our, or the general partner's, as applicable, percentage interest in our operating partnership will be increased on a proportionate basis based on the amount of the additional capital contributions and the value of our operating partnership at the time of the contributions. In addition, if we or the general partner contribute additional capital and receive additional operating partnership units for the capital contribution, the capital accounts of the partners may be adjusted upward or downward to reflect any unrealized gain or loss attributable to the properties as if there were an actual sale of the properties at the fair market value thereof. No person has any preemptive, preferential or other similar right with respect to making additional capital contributions or loans to our operating partnership or the issuance or sale of any operating partnership units or other partnership interests.

Our operating partnership could issue preferred partnership interests in connection with acquisitions of property or otherwise. Any such preferred partnership interests would have priority over common partnership interests with respect to distributions from our operating partnership, including the partnership interests that we own.

The general partner may cause our operating partnership to borrow money and to issue and guarantee debt as the general partner deems necessary for the conduct of the activities of our operating partnership. Such debt may be secured, among other things, by mortgages, deeds of trust, liens or encumbrances on the properties of our operating partnership.

The general partner is the tax matters partner and "partnership representative" of our operating partnership and, as the sole trustee of the general partner, we have the authority under the Code to handle tax audits on behalf of our operating partnership. In addition, as the sole trustee of the general partner, we have the authority to arrange for the preparation and filing of our operating partnership's tax returns and to make tax elections under the Code on behalf of our operating partnership. The foregoing provisions will generally be relevant only to the extent our operating partnership admits additional partners such that it becomes a partnership (rather than a disregarded entity) for U.S. federal income tax purposes.

Subject to any special allocations that may be required under the terms of any class or series of partnership units created in the future, the net income or net loss of our operating partnership is

generally allocated to the general partner and the limited partners of our operating partnership in accordance with their respective ownership of operating partnership units. However, in some cases, gains or losses may be disproportionately allocated to partners who have contributed property to or guaranteed debt of our operating partnership. The allocations described above are subject to special allocations relating to depreciation deductions and to compliance with the provisions of Sections 704(b) and 704(c) of the Code and the associated Treasury regulations. See "U.S. Federal Income Tax Considerations—Tax Aspects of Our Operating Partnership and any Subsidiary Partnerships and Disregarded Entities." The foregoing provisions will generally be relevant only to the extent our operating partnership admits additional partners such that it becomes a partnership (rather than a disregarded entity) for U.S. federal income tax purposes.

In addition, our operating partnership may from time to time issue LTIP units to persons who provide services to our company for such consideration or for no consideration as we may determine to be appropriate, and admit such persons as limited partners. The terms of the LTIP units are specified in Exhibit C to the partnership agreement, which addresses, among other things, vesting and forfeiture, allocations, distributions, redemption, conversion to common partnership units of our operating partnership ("OP Units"), voting rights and restrictions on transfer. In general, LTIP units are a class of partnership units of our operating partnership that, except as may be otherwise provided in the partnership agreement, our 2012 Restated Long Term Incentive Plan or any applicable award agreement, will be entitled to receive the same per unit distribution of operating income as the OP Units. The LTIP units may be subject to vesting requirements. Initially, each LTIP unit will have a capital account balance of zero and, therefore, will not have full parity with OP Units with respect to liquidating distributions. However, the partnership agreement provides that "book gain," or economic appreciation, in assets realized by our operating partnership as a result of the actual sale of all or substantially all of our operating partnership's assets or the revaluation of our operating partnership's assets as provided by applicable Treasury regulations will be allocated first to the holders of LTIP units until the capital account per LTIP unit is equal to the fair market value of a share of our common stock, subject to certain adjustments. The partnership agreement provides that our operating partnership's assets will be revalued upon the occurrence of certain events, including additional capital contributions, a liquidation of our operating partnership or the issuance of a partnership interest (including LTIP units).

Upon equalization of the capital accounts of the holders of LTIP units with the fair market value of the shares of our common stock, subject to certain adjustments, the LTIP units will achieve full parity with the OP Units for all purposes, including with respect to liquidating distributions. If such parity is reached, vested LTIP units will be convertible into an equal number of OP Units, and thereafter enjoy all the rights of OP Units. If a sale or revaluation of assets occurs at a time when our operating partnership's assets have appreciated sufficiently since the last revaluation, the LTIP units would achieve full parity with the OP Units upon such sale or revaluation. In the absence of sufficient appreciation in the value of our operating partnership's assets at the time of a sale or revaluation, full parity would not be reached. Consequently, an LTIP unit may never convert into an OP Unit if the value of our operating partnership's assets has not appreciated sufficiently between revaluation dates to equalize the capital account per LTIP unit to the fair market value of a share of our common stock, subject to certain adjustments. Until and unless parity is reached, the value for a given number of vested LTIP units will be less than the value of an equal number of shares of our common stock.

With respect to LTIP units that convert into OP Units, the partnership agreement provides that holders of OP Units are generally entitled to receive distributions on a pro rata basis in accordance with their respective OP Units (subject to the rights of the holders of any class of preferred partnership interests that may be authorized and issued in the future). Pursuant to the terms of the partnership agreement, holders of LTIP units are not entitled to the redemption rights described above unless, until and to the extent such LTIP units have been converted into OP Units.

We intend to cause the general partner of our operating partnership to manage our operating partnership in a manner that will enable us to maintain our qualification as a REIT and to minimize any U.S. federal income tax liability.

The partnership agreement provides that our operating partnership will assume and pay when due, or reimburse us for payment of, all costs and expenses relating to the operations of, or for the benefit of, our operating partnership.

Pursuant to the partnership agreement of our operating partnership, neither we nor the general partner may engage in, or cause or permit, a Termination Transaction, other than with the consent of limited partners (other than us, the general partner and entities controlled by us or the general partner, if there are any other limited partners) holding a majority of all the outstanding operating partnership units held by all partners (other than us, the general partner and entities controlled by us or the general partner, if there are any other limited partners) entitled to vote on or consent to such matter, or if the requirements discussed below are satisfied. A "Termination Transaction" means any direct or indirect transfer of all or any portion of our limited partnership interest in our operating partnership or any direct or indirect transfer of our interest in the general partner in connection with:

The consent of the limited partners to a Termination Transaction is not required if either:

Our operating partnership will continue in full force and effect until dissolved in accordance with its terms or as otherwise provided by law.

Maryland law permits a Maryland limited partnership to indemnify any partner, employee or agent from and against any and all claims whatsoever, except in the case of an action or failure to act by a partner that constitutes willful misconduct or recklessness, and subject to any standards or restrictions set forth in its partnership agreement. To the fullest extent permitted by applicable law, the partnership agreement requires our operating partnership to indemnify us, our directors, officers and employees, the general partner and its trustees, officers and employees, employees of our operating partnership and any other persons whom the general partner may designate, which we refer to collectively as "indemnitees", and each an "indemnitee", from and against any and all claims arising from or that relate to the operations of our operating partnership in which any indemnitee may be involved, or is threatened to be involved, as a party, witness or otherwise unless:

The general partner is not liable to our operating partnership or its partners except for fraud, willful misconduct or gross negligence, and no trustee, officer or agent of the general partner (including us, in our capacity as the sole trustee of the general partner), and none of our directors, officers or agents have any duties directly to our operating partnership or its partners, and will not be liable to our operating partnership or its partners for money damages by reason of their service as such.

The following summary of certain provisions of Maryland law and of our charter and bylaws does not purport to be complete and is subject to and qualified in its entirety by reference to Maryland law, including the MGCL, and our charter and bylaws. Copies of our charter and bylaws have been filed with the SEC and are incorporated by reference as exhibits to the registration statement of which this prospectus is a part. See "Where You Can Find More Information."

Our board of directors currently consists of eight directors. Our charter and bylaws provide that the number of directors constituting our board of directors may be increased or decreased only by a majority vote of our board of directors, provided that the number of directors may not be decreased to fewer than the minimum number required under the MGCL, nor increased to more than 15.

Subject to the terms of any class or series of preferred stock, vacancies on our board of directors may be filled only by a majority of the remaining directors, even if the remaining directors do not constitute a quorum, and any director elected to fill a vacancy will hold office for the remainder of the full term of the directorship in which the vacancy occurred and until his or her successor is duly elected and qualifies.

Each of our directors is elected by our stockholders to serve until the next annual meeting of our stockholders and until his or her successor is duly elected and qualifies. Holders of shares of our common stock have no right to cumulative voting in the election of directors. Consequently, the holders of a majority of the outstanding shares of our common stock can elect all of the directors then standing for election, and the holders of the remaining shares will not be able to elect any directors. Directors are elected by a plurality of all of the votes cast in the election of directors.

Our charter provides that a director may be removed only for cause (as defined in our charter) and only by the affirmative vote of a majority of the votes entitled to be cast generally in the election of directors. This provision, when coupled with the exclusive power of our board of directors to fill vacancies on our board of directors, precludes stockholders from removing incumbent directors (except for cause and upon a substantial affirmative vote) and filling the vacancies created by such removal with their own nominees.

Under the MGCL, certain "business combinations" (including a merger, consolidation, statutory share exchange or, in certain circumstances, an asset transfer or issuance or reclassification of equity securities) between a Maryland corporation and an interested stockholder (defined generally as any person who beneficially owns, directly or indirectly, 10% or more of the voting power of the corporation's outstanding voting stock or an affiliate or associate of the corporation who, at any time during the two-year period immediately prior to the date in question, was the beneficial owner of 10% or more of the voting power of the then-outstanding stock of the corporation) or an affiliate of such an interested stockholder are prohibited for five years after the most recent date on which the interested stockholder becomes an interested stockholder. Thereafter, any such business combination must generally be recommended by the board of directors of the corporation and approved by the affirmative vote of at least (i) 80% of the votes entitled to be cast by holders of outstanding shares of voting stock of the corporation and (ii) two-thirds of the votes entitled to be cast by holders of voting stock of the corporation, other than shares held by the interested stockholder with whom (or with whose affiliate) the business combination is to be effected or held by an affiliate or associate of the interested stockholder, unless, among other conditions, the corporation's common stockholders receive

a minimum price (as defined in the MGCL) for their shares and the consideration is received in cash or in the same form as previously paid by the interested stockholder for its shares. A person is not an interested stockholder under the statute if the board of directors approved in advance the transaction by which the person otherwise would have become an interested stockholder. A corporation's board of directors may provide that its approval is subject to compliance, at or after the time of approval, with any terms and conditions determined by the board.

Pursuant to the statute, our board of directors has by resolution exempted business combinations between us and any other person, provided that the business combination is first approved by our board of directors (including a majority of our directors who are not affiliates or associates of such person). Consequently, the five-year prohibition and the supermajority vote requirements will not apply to a business combination between us and any other person if the board of directors has first approved the combination. As a result, any person described in the preceding sentence may be able to enter into business combinations with us that may not be in the best interests of our stockholders, without compliance with the supermajority vote requirements and other provisions of the statute. We cannot assure you that our board of directors will not amend or repeal this resolution in the future.

The MGCL provides that holders of "control shares" of a Maryland corporation acquired in a "control share acquisition" have no voting rights with respect to such shares except to the extent approved by the affirmative vote of at least two-thirds of the votes entitled to be cast on the matter. Shares owned by the acquirer, an officer of the corporation or an employee of the corporation who is also a director of the corporation are excluded from shares entitled to vote on the matter.

"Control shares" are voting shares of stock that, if aggregated with all other such shares of stock owned by the acquirer, or in respect of which the acquirer is able to exercise or direct the exercise of voting power (except solely by virtue of a revocable proxy), would entitle the acquirer to exercise voting power in electing directors within one of the following ranges of voting power:

Control shares do not include shares that the acquiring person is then entitled to vote as a result of having previously obtained stockholder approval or shares acquired directly from the corporation. A "control share acquisition" means the acquisition of issued and outstanding control shares, subject to certain exceptions.

A person who has made or proposes to make a control share acquisition, upon satisfaction of certain conditions (including an undertaking to pay expenses and making an "acquiring person statement" as described in the MGCL), may compel the board of directors to call a special meeting of stockholders to be held within 50 days of demand to consider the voting rights of the shares. If no request for a meeting is made, the corporation may itself present the question at any stockholders meeting.

If voting rights are not approved at the meeting or if the acquiring person does not deliver an "acquiring person statement" as required by the statute, then, subject to certain conditions and limitations, the corporation may redeem for fair value any or all of the control shares (except those for which voting rights have previously been approved). Fair value is determined, without regard to the absence of voting rights for the control shares, as of the date of the last control share acquisition by the acquirer or, if a meeting of stockholders is held at which the voting rights of such shares are considered and not approved, as of the date of such meeting. If voting rights for control shares are approved at a

stockholders' meeting and the acquirer becomes entitled to vote a majority of the shares entitled to vote, all other stockholders may exercise appraisal rights. The fair value of the shares as determined for purposes of such appraisal rights may not be less than the highest price per share paid by the acquirer in the control share acquisition.

The control share acquisition statute does not apply to shares acquired in a merger, consolidation or statutory share exchange if the corporation is a party to the transaction or acquisitions approved or exempted by the charter or bylaws of the corporation.

Our bylaws contain a provision exempting from the control share acquisition statute any and all acquisitions by any person of shares of our stock. This provision may be amended or eliminated at any time in the future by our board of directors.

Subtitle 8 of Title 3 of the MGCL permits a Maryland corporation with a class of equity securities registered under the Exchange Act and at least three independent directors to elect to be subject, by provision in its charter or bylaws or a resolution of its board of directors and notwithstanding any contrary provision in the charter or bylaws, to any or all of five provisions of the MGCL that provide, respectively, for:

Pursuant to Subtitle 8, we have elected to provide that vacancies on our board may be filled only by the remaining directors and that directors elected by the board to fill vacancies will serve for the remainder of the full term of the directorship in which the vacancy occurred. Through provisions in our charter and bylaws unrelated to Subtitle 8, we already (i) vest in the board the exclusive power to fix the number of directorships and (ii) require, unless called by our chairman of the board, our chief executive officer, our president or our board of directors, the written request of stockholders entitled to cast a majority of all of the votes entitled to be cast at such a meeting to call a special meeting.

Pursuant to our bylaws, a meeting of our stockholders for the election of directors and the transaction of any business will be held annually on a date and at the time and place set by our board of directors. The chairman of our board of directors, our chief executive officer, our president or our board of directors may call a special meeting of our stockholders. Subject to the provisions of our bylaws, a special meeting of our stockholders to act on any matter that may properly be brought before a meeting of our stockholders must also be called by our secretary upon the written request of the stockholders entitled to cast a majority of all the votes entitled to be cast on such matter at the meeting and containing the information required by our bylaws. Our secretary will inform the requesting stockholders of the reasonably estimated cost of preparing and delivering the notice of meeting (including our proxy materials), and the requesting stockholder must pay such estimated cost before our secretary is required to prepare and deliver the notice of the special meeting.

Except for those amendments permitted to be made without stockholder approval under Maryland law or our charter, our charter generally may be amended only if the amendment is first declared advisable by our board of directors and thereafter approved by the affirmative vote of stockholders entitled to cast a majority of all of the votes entitled to be cast on the matter.

Our board of directors has the power to adopt, alter or repeal any provision of our bylaws and to make new bylaws. In addition, stockholders may alter or repeal any provision of our bylaws and adopt new bylaws with the approval by a majority of the votes entitled to be cast on the matter.

Our bylaws require, subject to limited exceptions, that any derivative action or proceeding brought on our behalf, any action asserting a claim of breach of any duty owed by any of our directors, officers or other employees to us or our stockholders and other similar actions, may be brought only in specified courts in the State of Maryland. Although we believe this provision will benefit us by limiting costly and time-consuming litigation in multiple forums and by providing increased consistency in the application of Maryland law in the types of lawsuits to which it applies, the provision may have the effect of discouraging lawsuits against us or our directors, officers and other employees.

Under the MGCL, a Maryland corporation generally may not dissolve, merge or consolidate with, or convert to, another entity, sell all or substantially all of its assets or engage in a statutory share exchange unless the action is declared advisable by the board of directors and approved by the affirmative vote of stockholders entitled to cast at least two-thirds of the votes entitled to be cast on the matter, unless a lesser percentage (but not less than a majority of all of the votes entitled to be cast on the matter) is specified in the corporation's charter. Our charter provides that these actions must be approved by a majority of all of the votes entitled to be cast on the matter.

The dissolution of our company must be declared advisable by a majority of our entire board of directors and approved by the affirmative vote of the holders of a majority of all of the votes entitled to be cast on the matter.

Our bylaws provide that, with respect to an annual meeting of our stockholders, nominations of individuals for election to our board of directors and the proposal of other business to be considered by our stockholders may be made only (i) pursuant to our notice of the meeting, (ii) by or at the direction of our board of directors or (iii) by any stockholder who was a stockholder of record at the record date set by the board of directors for the purpose of determining stockholders entitled to vote at the meeting, at the time of giving the notice required by our bylaws and at the time of the meeting (or any postponement or adjournment thereof), who is entitled to vote at the meeting on such business or in the election of such nominee and has provided notice to us within the time period, and containing the information and other materials, specified in the advance notice provisions of our bylaws.

With respect to special meetings of stockholders, only the business specified in our notice of meeting may be brought before the meeting. Nominations of individuals for election to our board of directors may be made only (i) by or at the direction of our board of directors or (ii) if the meeting has been called for the purpose of electing directors, by any stockholder who was a stockholder of record at the record date set by the board of directors for the purpose of determining stockholders

entitled to vote at the meeting, at the time of giving the notice required by our bylaws and at the time of the meeting (or any postponement or adjournment thereof), who is entitled to vote at the meeting in the election of each such nominee and who has provided notice to us within the time period, and containing the information and other materials, specified in the advance notice provisions of our bylaws.

The advance notice procedures of our bylaws provide that, to be timely, a stockholder's notice with respect to director nominations or other proposals for an annual meeting must be delivered to our corporate secretary at our principal executive office not earlier than the 150th day nor later than 5:00 p.m., Eastern Time, on the 120th day prior to the first anniversary of the date of the proxy statement for our preceding year's annual meeting. In the event that the date of the annual meeting is advanced or delayed by more than 30 days from the first anniversary of the date of the preceding year's annual meeting, to be timely, a stockholder's notice must be delivered not earlier than the 150th day prior to the date of such annual meeting and not later than 5:00 p.m., Eastern Time, on the close of business on the later of the 120th day prior to the date of such annual meeting or the tenth day following the day on which public announcement of the date of such meeting is first made.

Our charter provides that our board of directors may authorize us to revoke or otherwise terminate our REIT election, without approval of our stockholders, if it determines that it is no longer in our best interests to continue to qualify as a REIT.

Our charter and bylaws and Maryland law contain provisions that may delay, defer or prevent a change in control or other transaction that might involve a premium price for shares of our common stock or otherwise be in the best interests of our stockholders, including business combination provisions, supermajority vote requirements and advance notice requirements for director nominations and other stockholder proposals. Likewise, if the provision in our bylaws opting out of the control share acquisition provisions of the MGCL were rescinded or if we were to opt in to the classified board or other provisions of Subtitle 8, these provisions of the MGCL could have similar anti-takeover effects.

Maryland law permits a Maryland corporation to include in its charter a provision limiting the liability of its directors and officers to the corporation and its stockholders for money damages, except for liability resulting from (i) actual receipt of an improper benefit or profit in money, property or services or (ii) active and deliberate dishonesty that is established by a final judgment and that is material to the cause of action. Our charter contains a provision that eliminates the liability of our directors and officers to the maximum extent permitted by Maryland law.

The MGCL requires us (unless our charter provides otherwise, which our charter does not) to indemnify a director or officer who has been successful, on the merits or otherwise, in the defense of any proceeding to which he or she is made a party by reason of his or her service in that capacity. The MGCL permits us to indemnify our present and former directors and officers, among others, against judgments, penalties, fines, settlements and reasonable expenses actually incurred by them in connection with any proceeding to which they may be made or threatened to be made a party by reason of their service in those or other capacities unless it is established that:

Under the MGCL, we may not indemnify a director or officer in a suit by us or in our right in which the director or officer was adjudged liable to us or in a suit in which the director or officer was adjudged liable on the basis that personal benefit was improperly received. A court may order indemnification if it determines that the director or officer is fairly and reasonably entitled to indemnification, even though the director or officer did not meet the prescribed standard of conduct or was adjudged liable on the basis that personal benefit was improperly received. However, indemnification for an adverse judgment in a suit by us or in our right, or for a judgment of liability on the basis that personal benefit was improperly received, is limited to expenses.

In addition, the MGCL permits us to advance reasonable expenses to a director or officer upon our receipt of:

Our charter authorizes us to obligate ourselves, and our bylaws obligate us, to the maximum extent permitted by Maryland law in effect from time to time, to indemnify and, without requiring a preliminary determination of the ultimate entitlement to indemnification, pay or reimburse reasonable expenses in advance of final disposition of a proceeding to:

Our charter and bylaws also permit us to indemnify and advance expenses to any person who served a predecessor of ours in any of the capacities described above and to any employee or agent of our company or a predecessor of our company.

We have entered into indemnification agreements with each of our directors and executive officers that provide for indemnification to the maximum extent permitted by Maryland law.

The partnership agreement provides that we, our directors, officers and employees, the general partner and its trustees, officers and employees, employees of our operating partnership and any other persons whom the general partner may designate are indemnified to the fullest extent permitted by law. See "Description of the Partnership Agreement of CyrusOne LP—Indemnification and Limitation of Liability."

Insofar as the foregoing provisions permit indemnification of directors, officers or persons controlling us for liability arising under the Securities Act, we have been informed that, in the opinion of the SEC, this indemnification is against public policy as expressed in the Securities Act and is therefore unenforceable.

The following is a summary of the material U.S. federal income tax consequences of an investment in our common stock. Supplemental U.S. federal income tax considerations relevant to the ownership of the other securities offered by this prospectus may be provided in the prospectus supplement that relates to those securities. For purposes of this section under the heading "U.S. Federal Income Tax Considerations," references to "CyrusOne Inc.," "we," "our" and "us" generally mean only CyrusOne Inc. and not its subsidiaries or other lower-tier entities, except as otherwise indicated, and references to "tenants" are to persons who are treated as lessees of real property for purposes of the REIT requirements including, in general, persons who are referred to as "customers" elsewhere in this prospectus. This summary is based upon the Code, the regulations promulgated by the Treasury, rulings and other administrative pronouncements issued by the IRS, and judicial decisions, all as currently in effect, and all of which are subject to differing interpretations or to change, possibly with retroactive effect. No assurance can be given that the IRS would not assert, or that a court would not sustain, a position contrary to any of the tax consequences described below. The summary is also based upon the assumption that we and our subsidiaries and affiliated entities will operate in accordance with our and their applicable organizational documents. This summary is for general information only and is not tax advice. It does not discuss any state, local or non-U.S. tax consequences relevant to us or an investment in any securities offered by this prospectus, and it does not purport to discuss all aspects of U.S. federal income taxation that may be important to a particular investor in light of its investment or tax circumstances or to investors subject to special tax rules, such as:

This summary assumes that investors will hold their shares of our common stock as a capital asset, which generally means property held for investment.

The U.S. federal income tax treatment of holders of our common stock depends in some instances on determinations of fact and interpretations of complex provisions of U.S. federal income tax law for which no clear precedent or authority may be available. In addition, the tax consequences to any particular stockholder of holding or disposing of our common stock will depend on the stockholder's particular tax circumstances. You are urged to consult your tax advisor regarding the U.S. federal, state, local, and foreign income and other tax consequences to you in light of your particular investment or tax circumstances of acquiring, holding, exchanging, or otherwise disposing of our common stock.

We have elected to be treated as a REIT commencing with our taxable year ended December 31, 2013, and intend to continue to operate in a manner that will allow us to qualify as a REIT.

The law firm of Skadden, Arps, Slate, Meagher & Flom LLP has acted as our special REIT tax counsel ("Special Tax Counsel"), and has provided us an opinion to the effect that, commencing with our taxable year ended December 31, 2013, we have been organized and have operated in conformity with the requirements for qualification and taxation as a REIT under the Code, and our proposed method of operation will enable us to meet the requirements for qualification and taxation as a REIT. It must be emphasized that the opinion of Special Tax Counsel is based on various assumptions relating to our organization and operation, and is conditioned upon fact-based representations and covenants made by our management regarding our organization, assets, and income, and the present and future conduct of our business operations. While we intend to operate so that we will continue to qualify as a REIT, given the highly complex nature of the rules governing REITs, the ongoing importance of factual determinations, and the possibility of future changes in our circumstances, no assurance can be given by Special Tax Counsel or by us that we will qualify as a REIT for any particular year. The opinion is expressed as of the date issued. Special Tax Counsel has no obligation to advise us or our stockholders of any subsequent change in the matters stated, represented or assumed, or of any subsequent change in the applicable law. You should be aware that opinions of counsel are not binding on the IRS, and no assurance can be given that the IRS will not challenge the conclusions set forth in such opinions.

Qualification and taxation as a REIT depend on our ability to meet on a continuing basis, through actual operating results, distribution levels, diversity of stock ownership, and various qualification requirements imposed upon REITs by the Code, all the results of which have not been and will not be reviewed by Special Tax Counsel. Our ability to qualify as a REIT also requires that we satisfy certain asset tests, some of which depend upon the fair market values of assets that we own directly or indirectly. Such values may not be susceptible to a precise determination. Accordingly, no assurance can be given that the actual results of our operations for any taxable year have satisfied or will satisfy such requirements for qualification and taxation as a REIT.

We have received a private letter ruling from the IRS with respect to certain issues relevant to our qualification as a REIT. In general, the ruling provides, subject to the terms and conditions contained therein, that certain structural components of our properties (e.g., relating to the provision of electricity, HVAC, regulation of humidity, security and fire protection, and telecommunication services) and intangible assets, and certain services that we or CBI may provide, directly or through subsidiaries, to our tenants, will not adversely affect our qualification as a REIT. Although we may generally rely upon the ruling, no assurance can be given that the IRS will not challenge our qualification as a REIT on the basis of other issues or facts outside the scope of the ruling.

As indicated above, our qualification and taxation as a REIT depend upon our ability to meet, on a continuing basis, various qualification requirements imposed upon REITs by the Code. The material qualification requirements are summarized below under "—Requirements for Qualification—General." While we intend to operate so that we continue to qualify as a REIT, no assurance can be given that the IRS will not challenge our qualification, or that we will be able to operate in accordance with the REIT requirements in the future. See "—Failure to Qualify."

Provided that we qualify as a REIT, generally we will be entitled to a deduction for dividends that we pay and therefore will not be subject to U.S. federal corporate income tax on our net taxable income that is currently distributed to our stockholders. This treatment substantially eliminates the "double taxation" at the corporate and stockholder levels that generally results from an investment in a C corporation. A "C corporation" is a corporation that generally is required to pay tax at the corporate

level. Double taxation means taxation once at the corporate level when income is earned and once again at the stockholder level when the income is distributed. In general, the income that we generate is taxed only at the stockholder level upon a distribution of dividends to our stockholders.

Any net operating losses, foreign tax credits and other tax attributes generally do not pass through to our stockholders, subject to special rules for certain items such as the capital gains that we recognize. See "—Taxation of Stockholders—Taxation of Taxable U.S. Stockholders—Distributions."

If we qualify as a REIT, we will nonetheless be subject to U.S. federal tax in the following circumstances:

In addition, we and our subsidiaries may be subject to a variety of taxes, including payroll taxes and state, local, and foreign income, property, gross receipts and other taxes on our assets and operations. We could also be subject to tax in situations and on transactions not presently contemplated.

The Code provides that conditions (1) through (4) must be met during the entire taxable year, and that condition (5) must be met during at least 335 days of a taxable year of 12 months, or during a proportionate part of a shorter taxable year. Conditions (5) and (6) need not be met during a corporation's initial tax year as a REIT (which, in our case, was 2013). Our charter provides restrictions regarding the ownership and transfers of our stock, which are intended to assist us in satisfying the stock ownership requirements described in conditions (5) and (6) above. These restrictions, however, may not ensure that we will, in all cases, be able to satisfy the share ownership requirements described in conditions (5) and (6) above. If we fail to satisfy these share ownership requirements, except as provided in the next sentence, our status as a REIT will terminate. If, however, we comply with the rules contained in applicable Treasury regulations that require us to ascertain the actual ownership of our shares and we do not know, or would not have known through the exercise of reasonable diligence, that we failed to meet the requirement described in condition (6) above, we will be treated as having met this requirement.

To monitor compliance with the stock ownership requirements, we generally are required to maintain records regarding the actual ownership of our stock. To do so, we must demand written statements each year from the record holders of significant percentages of our stock pursuant to which the record holders must disclose the actual owners of the stock (i.e., the persons required to include our dividends in their gross income). We must maintain a list of those persons failing or refusing to comply with this demand as part of our records. We could be subject to monetary penalties if we fail to comply with these record-keeping requirements. If you fail or refuse to comply with the demands, you

will be required by Treasury regulations to submit a statement with your tax return disclosing your actual ownership of our stock and other information.

In addition, a corporation generally may not elect to become a REIT unless its taxable year is the calendar year. We adopted December 31 as our year-end and thereby satisfy this requirement.

Ownership of Partnership Interests. If we are a partner in an entity that is treated as a partnership for U.S. federal income tax purposes, Treasury regulations provide that we are deemed to own our proportionate share of the partnership's assets, and to earn our proportionate share of the partnership's income, for purposes of the asset and gross income tests applicable to REITs. Our proportionate share of a partnership's assets and income is based on our capital interest in the partnership (except that for purposes of the 10% value test, described below, our proportionate share of the partnership's assets is based on our proportionate interest in the equity and certain debt securities issued by the partnership). In addition, the assets and gross income of the partnership are deemed to retain the same character in our hands. Thus, our proportionate share of the assets and items of income of any of our subsidiary partnerships will be treated as our assets and items of income for purposes of applying the REIT requirements.

We have control of any subsidiary entity treated as a partnership and intend to operate such entities in a manner consistent with the requirements for our qualification as a REIT. If we become a limited partner or non-managing member in any entity treated as a partnership and such entity takes or expects to take actions that could jeopardize our status as a REIT or require us to pay tax, we may be forced to dispose of our interest in such entity. In addition, it is possible that an entity treated as a partnership could take an action which could cause us to fail a gross income or asset test, and that we would not become aware of such action in time to dispose of our interest in such entity or take other corrective action on a timely basis. In that case, we could fail to qualify as a REIT unless we were entitled to relief, as described below.

Disregarded Subsidiaries. If we own a corporate subsidiary that is a "qualified REIT subsidiary," that subsidiary is generally disregarded as a separate entity for U.S. federal income tax purposes, and all of the subsidiary's assets, liabilities and items of income, deduction and credit are treated as our assets, liabilities and items of income, deduction and credit, including for purposes of the gross income and asset tests applicable to REITs. A qualified REIT subsidiary is any corporation, other than a TRS (as described below), that is directly or indirectly wholly-owned by a REIT. Other entities that are wholly-owned by us (either directly or through other disregarded entities), including single member limited liability companies that have not elected to be taxed as corporations for U.S. federal income tax purposes, are also generally disregarded as separate entities for U.S. federal income tax purposes, including for purposes of the REIT income and asset tests. For example, our operating partnership is currently a disregarded entity. Disregarded subsidiaries, along with any partnerships in which we hold an equity interest, are sometimes referred to herein as "pass-through subsidiaries."

In the event that a disregarded subsidiary of ours ceases to be wholly-owned—for example, if any equity interest in our operating partnership or other disregarded subsidiary is acquired by a person other than us or another disregarded subsidiary of ours—the subsidiary's separate existence would no longer be disregarded for U.S. federal income tax purposes. Instead, the subsidiary would have multiple owners and would be treated as either a partnership or a taxable corporation. Such an event could, depending on the circumstances, adversely affect our ability to satisfy the various asset and gross income requirements applicable to REITs, including the requirement that REITs generally may not own, directly or indirectly, more than 10% of the securities of another corporation. See "—Asset Tests" and "—Income Tests."

Taxable REIT Subsidiaries. In general, we may jointly elect with a subsidiary corporation, whether or not wholly-owned, to treat such subsidiary corporation as a TRS. We generally may not own more than 10% of the securities of a taxable corporation, as measured by voting power or value, unless we and such corporation elect to treat such corporation as a TRS. The separate existence of a TRS or other taxable corporation is not ignored for U.S. federal income tax purposes. Accordingly, a TRS or other taxable subsidiary corporation generally is subject to corporate income tax on its earnings, which may reduce the cash flow that we and our subsidiaries generate in the aggregate, and may reduce our ability to make distributions to our stockholders.

We are not treated as holding the assets of a TRS or other taxable subsidiary corporation or as receiving any income that the subsidiary earns. Rather, the stock issued by a taxable subsidiary corporation to us is an asset in our hands, and we treat the dividends paid to us from such taxable subsidiary corporation, if any, as income. This treatment can affect our income and asset test calculations, as described below. Because we do not include the assets and income of TRSs or other taxable subsidiary corporations on a look-through basis in determining our compliance with the REIT requirements, we may use such entities to undertake indirectly activities that the REIT rules might otherwise preclude us from doing directly or through pass-through subsidiaries. For example, we may use TRSs or other taxable subsidiary corporations to perform services or conduct activities that give rise to certain categories of income such as management fees, or to conduct activities that, if conducted by us directly, would be treated in our hands as prohibited transactions.

The TRS rules impose a 100% excise tax on transactions between a TRS and its parent REIT or the REIT's tenants that are not conducted on an arm's length basis. We intend that all of our transactions with our TRSs, if any, will be conducted on an arm's length basis.

Subsidiary REITs. We own certain of our assets through a subsidiary that is intended to be treated as a REIT. Our stock of any subsidiary REIT will generally be treated as a qualifying real estate asset for purposes of the REIT asset requirements (see "—Asset Tests" below), and any dividend income or gains derived by us from such stock will generally be treated as income that qualifies for purposes of the REIT 95% and 75% income requirements (see "—Income Tests" below), provided, in each case, that such subsidiary qualifies as a REIT. We and any subsidiary REIT are separate entities, each of which intends to qualify as a REIT, and each of which must independently satisfy the various REIT qualification requirements as described herein. If our subsidiary REIT were to fail to qualify as a REIT, it would then be a regular taxable corporation, and its income would be subject to U.S. federal income tax. In addition, a failure of such subsidiary to qualify as a REIT would likely have an adverse effect on our ability to comply with the REIT asset and income requirements described below, and thus our ability to qualify as a REIT.

Commencing in taxable years beginning after December 31, 2017, Section 163(j) of the Code limits the deductibility of net interest expense paid or accrued on debt properly allocable to a trade or business to 30% of "adjusted taxable income," subject to certain exceptions. Any deduction in excess of the limitation is carried forward and may be used in a subsequent year, subject to the 30% limitation. Adjusted taxable income is determined without regard to certain deductions, including those for net interest expense, net operating loss carryforwards and, for taxable years beginning before January 1, 2022, depreciation, amortization and depletion. Provided the taxpayer makes a timely election (which is irrevocable), the 30% limitation does not apply to a trade or business involving real property development, redevelopment, construction, reconstruction, rental, operation, acquisition, conversion, disposition, management, leasing or brokerage. If we make this election, we must use a generally less favorable depreciation system under the Code for our real property (including certain improvements). If we do not make the election or if the election is determined not to be available with respect to all or certain of our business activities, the new interest deduction limitation could change the amount of

REIT taxable income we have and thus change the amount of distributions we must make to comply with the REIT requirements and avoid incurring corporate level tax. In addition, the foregoing limitations on the deduction of interest expense (including, if applicable, elections with respect thereto) will apply to our TRSs or other regarded subsidiary entities.

In order to qualify as a REIT, we must satisfy two gross income requirements on an annual basis. First, at least 75% of our gross income for each taxable year, excluding gross income from sales of inventory or dealer property in "prohibited transactions," discharge of indebtedness and certain hedging transactions, generally must be derived from "rents from real property," gains from the sale of real property, mortgages on real property, and shares in other REITs, interest income derived from mortgage loans secured by real property (including certain types of mortgage-backed securities), dividends received from other REITs, and specified income from temporary investments. Second, at least 95% of our gross income in each taxable year, excluding gross income from prohibited transactions, discharge of indebtedness and certain hedging transactions, must be derived from some combination of income that qualifies under the 75% gross income test described above, as well as other dividends, interest, and gain from the sale or disposition of stock or securities, which need not have any relation to real property. Income and gain from certain hedging transactions will be excluded from both the numerator and the denominator for purposes of both the 75% and 95% gross income tests.

Rents from Real Property. Rents we receive from a tenant will qualify as "rents from real property" for the purpose of satisfying the gross income requirements for a REIT described above only if all of the conditions described below are met.

A significant portion of the value of our properties is attributable to structural components related to the provision of electricity, heating ventilation and air conditioning, regulation of humidity, security and fire protection, and telecommunications infrastructure. In addition, we or our affiliates will provide certain services to tenants of our properties. We expect that our structural components will be treated as real property for purposes of the REIT gross income tests, and we intend to structure the provision of services in a manner that does not prevent our rental income from qualifying as "rents from real property." We have received a private letter ruling from the IRS with respect to certain issues relevant to our qualification as a REIT. In general, the ruling provides, subject to the terms and conditions contained therein, that certain structural components of our properties (e.g., relating to the provision of electricity, HVAC, regulation of humidity, security and fire protection, and telecommunication services), and certain services that we or CBI may provide, directly or through subsidiaries, to our tenants, will not adversely affect our qualification as a REIT. Although we may generally rely upon the ruling, no assurance can be given that the IRS will not challenge our qualification as a REIT on the basis of other issues or facts outside the scope of the ruling. In addition, the ruling may not apply to our subsidiary REIT, which was formed after our receipt of the ruling.

We intend to cause any services that are not "usually or customarily rendered," or that are for the benefit of a particular tenant in connection with the rental of real property, to be provided through a TRS or through an "independent contractor." However, no assurance can be given that the IRS will concur with our determination as to whether a particular service is usual or customary, or otherwise in this regard.

Interest Income. Interest income constitutes qualifying mortgage interest for purposes of the 75% gross income test (as described above) to the extent that the obligation upon which such interest is paid is secured by a mortgage on real property or an interest in real property. If we receive interest income with respect to a mortgage loan that is secured by both real property and other property, and the highest principal amount of the loan outstanding during a taxable year exceeds the fair market value of the real property on the date that we acquired or originated the mortgage loan, the interest income will generally be apportioned between the real property and the other collateral, and our income from the arrangement will qualify for purposes of the 75% gross income test only to the extent that the interest is allocable to the real property. In certain cases, personal property collateral securing a loan that we hold may be treated as real property for purposes of the foregoing rules. Even if a loan is not secured by real property, or is undersecured, the income that it generates may nonetheless qualify for purposes of the 95% gross income test. For these purposes, the term "interest" generally does not include any amount received or accrued, directly or indirectly, if the determination of all or some of the amount depends in any way on the income or profits of any person. However, an amount received or accrued generally will not be excluded from the term "interest" solely by reason of being based on a fixed percentage or percentages of receipts or sales.

Dividend Income. We may directly or indirectly receive distributions from TRSs or other corporations that are not REITs or qualified REIT subsidiaries. These distributions generally are

treated as dividend income to the extent of the earnings and profits of the distributing corporation. Such distributions will generally constitute qualifying income for purposes of the 95% gross income test, but not for purposes of the 75% gross income test. Any dividends that we receive from another REIT, however, will be qualifying income for purposes of both the 95% and 75% gross income tests.

Fee Income. Any fee income that we earn will generally not be qualifying income for purposes of either gross income test. Any fees earned by a TRS, however, will not be included for purposes of our gross income tests.

Hedging Transactions. Any income or gain that we or our pass-through subsidiaries derive from instruments that hedge certain specified risks, such as the risk of changes in interest rates, will be excluded from gross income for purposes of both the 75% and 95% gross income tests, provided that specified requirements are met, including the requirement that the instrument is entered into during the ordinary course of our business and that the instrument be properly identified as a hedge along with the risk that it hedges within prescribed time periods. Income and gain from all other hedging transactions will not be qualifying income for either the 95% or 75% gross income test.

Failure to Satisfy the Gross Income Tests. If we fail to satisfy one or both of the 75% or 95% gross income tests for any taxable year, we may still qualify as a REIT for such year if we are entitled to relief under applicable provisions of the Code. These relief provisions will be generally available if (i) our failure to meet these tests was due to reasonable cause and not due to willful neglect and (ii) following our identification of the failure to meet the 75% or 95% gross income test for any taxable year, we file a schedule with the IRS setting forth each item of our gross income for purposes of the 75% or 95% gross income test for such taxable year in accordance with Treasury regulations, which have not yet been issued. It is not possible to state whether we would be entitled to the benefit of these relief provisions in all circumstances. If these relief provisions are inapplicable to a particular set of circumstances, we will not qualify as a REIT. Even if these relief provisions apply, and we retain our status as a REIT, the Code imposes a tax based upon the amount by which we fail to satisfy the particular gross income test.

At the close of each calendar quarter, we must also satisfy five tests relating to the nature of our assets. First, at least 75% of the value of our total assets must be represented by some combination of "real estate assets," cash, cash items, U.S. government securities, and, under some circumstances, stock or debt instruments purchased with new capital. For this purpose, real estate assets include interests in real property (and certain ancillary personal property), stock of other corporations that qualify as REITs, some kinds of mortgage-backed securities and mortgage loans, and debt instruments (whether or not secured by real property) that are issued by a "publicly offered REIT" (i.e., a REIT that is required to file annual and periodic reports with the SEC under the Exchange Act). Assets that do not qualify for purposes of the 75% asset test are subject to the additional asset tests described below.

Second, the value of any one issuer's securities that we own may not exceed 5% of the value of our total assets.

Third, we may not own more than 10% of any one issuer's outstanding securities, as measured by either voting power or value. The 5% and 10% asset tests do not apply to securities of TRSs and qualified REIT subsidiaries and the value prong of the 10% asset test does not apply to "straight debt" having specified characteristics and to certain other securities described below. Solely for purposes of the value prong of the 10% asset test, the determination of our interest in the assets of a partnership or limited liability company in which we own an interest will be based on our proportionate interest in any securities issued by the partnership or limited liability company, excluding for this purpose certain securities described in the Code.

Fourth, the aggregate value of all securities of TRSs that we hold may not exceed 20% of the value of our total assets.

Fifth, no more than 25% of the total value of our assets may be represented by "nonqualified publicly offered REIT debt instruments" (i.e., real estate assets that would cease to be real estate assets if debt instruments issued by publicly offered REITs were not included in the definition of real estate assets).

Notwithstanding the general rule, as noted above, that for purposes of the REIT income and asset tests we are treated as owning our proportionate share of the underlying assets of a subsidiary partnership, if we hold indebtedness issued by a partnership, the indebtedness will be subject to, and may cause a violation of, the asset tests unless the indebtedness is a qualifying mortgage asset or other conditions are met. Similarly, although stock of another REIT is a qualifying asset for purposes of the REIT asset tests, any non-mortgage debt that is issued by non-publicly offered REIT may not so qualify (although such debt will not be treated as "securities" for purposes of the value prong of the 10% asset test, as explained below).

Certain securities will not cause a violation of the value prong of the 10% asset test described above. Such securities include instruments that constitute "straight debt," which term generally excludes, among other things, securities having contingency features. A security does not qualify as "straight debt" where a REIT (or a controlled TRS of the REIT) owns other securities of the same issuer which do not qualify as straight debt, unless the value of those other securities constitute, in the aggregate, 1% or less of the total value of that issuer's outstanding securities. In addition to straight debt, the Code provides that certain other securities will not violate the value prong of the 10% asset test. Such securities include (i) any loan made to an individual or an estate, (ii) certain rental agreements pursuant to which one or more payments are to be made in subsequent years (other than agreements between a REIT and certain persons related to the REIT under attribution rules), (iii) any obligation to pay rents from real property, (iv) securities issued by governmental entities that are not dependent in whole or in part on the profits of (or payments made by) a nongovernmental entity, (v) any security (including debt securities) issued by another REIT and (vi) any debt instrument issued by a partnership if the partnership's income is of a nature that it would satisfy the 75% gross income test described above under "—Income Tests." In applying the value prong of the 10% asset test, a debt security issued by a partnership is not taken into account to the extent, if any, of the REIT's proportionate interest in the equity and certain debt securities issued by that partnership.

No independent appraisals have been obtained to support our conclusions as to the value of our total assets or the value of any particular security or securities. Moreover, the values of some assets may not be susceptible to a precise determination, and values are subject to change in the future. Furthermore, the proper classification of an instrument as debt or equity for U.S. federal income tax purposes may be uncertain in some circumstances, which could affect the application of the REIT asset requirements. Accordingly, there can be no assurance that the IRS will not contend that our interests in our subsidiaries or in the securities of other issuers will not cause a violation of the REIT asset tests.

However, certain relief provisions are available to allow REITs to satisfy the asset requirements or to maintain REIT qualification notwithstanding certain violations of the asset tests and other

requirements. For example, if we should fail to satisfy the asset tests at the end of a calendar quarter such a failure would not cause us to lose our REIT qualification if we (i) satisfied the asset tests at the close of the preceding calendar quarter and (ii) the discrepancy between the value of our assets and the asset requirements was not wholly or partly caused by an acquisition of non-qualifying assets, but instead arose from changes in the relative market values of our assets. If the condition described in clause (ii) were not satisfied, we still could avoid disqualification by eliminating any discrepancy within 30 days after the close of the calendar quarter in which it arose or by making use of the relief provisions described above.

In the case of de minimis violations of the 10% and 5% asset tests, a REIT may maintain its qualification despite a violation of such requirements if (i) the value of the assets causing the violation does not exceed the lesser of 1% of the REIT's total assets and $10,000,000 and (ii) the REIT either disposes of the assets causing the failure within six months after the last day of the quarter in which it identifies the failure, or the relevant tests are otherwise satisfied within that time frame.

Even if we did not qualify for the foregoing relief provisions, one additional provision allows a REIT that fails one or more of the asset tests to nevertheless maintain its REIT qualification if (i) the REIT provides the IRS with a description of each asset causing the failure, (ii) the failure is due to reasonable cause and not willful neglect, (iii) the REIT pays a tax equal to the greater of (a) $50,000 per failure and (b) the product of the net income generated by the assets that caused the failure multiplied by the highest applicable corporate tax rate and (iv) the REIT either disposes of the assets causing the failure within six months after the last day of the quarter in which it identifies the failure, or otherwise satisfies the relevant asset tests within that time frame.

In order to qualify as a REIT, we are required to annually distribute dividends, other than capital gain dividends, to our stockholders in an amount at least equal to:

We generally must make these distributions in the taxable year to which they relate, or in the following taxable year if declared before we timely file our tax return for the year and if paid with or before the first regular dividend payment after such declaration. These distributions will be treated as received by our stockholders in the year in which paid.

To the extent that we distribute at least 90%, but less than 100%, of our REIT taxable income, as adjusted, we will be subject to tax at ordinary corporate tax rates on the retained portion. We may elect to retain, rather than distribute, some or all of our net long-term capital gains and pay tax on such gains. In this case, we could elect for our stockholders to include their proportionate shares of such undistributed long-term capital gains in income, and to receive a corresponding credit for their share of the tax that we paid. Our stockholders would then increase the adjusted basis of their stock by the difference between (i) the amounts of capital gain dividends that we designated and that they include in their taxable income, and (ii) the tax that we paid on their behalf with respect to that income.

To the extent that in the future we may have available net operating losses carried forward from prior tax years, such losses may, subject to limitations, reduce the amount of distributions that we must make in order to comply with the REIT distribution requirements. Such losses, however, will generally not affect the tax treatment to our stockholders of any distributions that are actually made. See "—Taxation of Stockholders—Taxation of Taxable U.S. Stockholders—Distributions."

If we fail to distribute during each calendar year at least the sum of (i) 85% of our ordinary income for such year, (ii) 95% of our capital gain net income for such year and (iii) any undistributed net taxable income from prior periods, we will be subject to a non-deductible 4% excise tax on the excess of such required distribution over the sum of (a) the amounts actually distributed, plus (b) the amounts of income we retained and on which we have paid corporate income tax.

We expect that our REIT taxable income will be less than our cash flow because of depreciation and other non-cash charges included in computing REIT taxable income. Accordingly, we anticipate that we generally will have sufficient cash or liquid assets to enable us to satisfy the distribution requirements described above. However, from time to time, we may not have sufficient cash or other liquid assets to meet these distribution requirements due to timing differences between the actual receipt of income and actual payment of deductible expenses, and the inclusion of income and deduction of expenses in determining our taxable income. In addition, we may decide to retain our cash, rather than distribute it, in order to repay debt, acquire assets, or for other reasons. If these timing differences occur, we may sell assets, borrow funds to pay dividends or pay dividends through the distribution of other property (including shares of our stock) in order to meet the distribution requirements, while preserving our cash.

If our taxable income for a particular year is subsequently determined to have been understated, we may be able to rectify a resultant failure to meet the distribution requirements for a year by paying "deficiency dividends" to stockholders in a later year, which may be included in our deduction for dividends paid for the earlier year. In this case, we may be able to avoid losing REIT qualification or being taxed on amounts distributed as deficiency dividends, subject to the 4% excise tax described above. We will be required to pay interest based on the amount of any deduction taken for deficiency dividends.

For purposes of the 90% distribution requirement and excise tax described above, any dividend that we declare in October, November or December of any year and that is payable to a stockholder of record on a specified date in any such month will be treated as both paid by us and received by the stockholder on December 31 of such year, provided that we actually pay the dividend before the end of January of the following calendar year.

Net income that we derive from a prohibited transaction is subject to a 100% tax. The term "prohibited transaction" generally includes a sale or other disposition of property (other than foreclosure property, as discussed below) that is held as inventory or primarily for sale to customers in the ordinary course of a trade or business. We intend to conduct our operations so that no asset that we own (or are treated as owning) will be treated as, or as having been, held as inventory or for sale to customers, and that a sale of any such asset will not be treated as having been in the ordinary course of our business. Whether property is held as inventory or "primarily for sale to customers in the ordinary course of a trade or business" depends on the particular facts and circumstances. No assurance can be given that any property that we sell will not be treated as inventory or property held for sale to customers, or that we can comply with certain safe-harbor provisions of the Code that would prevent such treatment. The 100% tax does not apply to gains from the sale of property that is held through a TRS or other taxable corporation, although such income will be subject to tax in the hands of the

corporation at regular corporate rates. We intend to structure our activities to avoid prohibited transaction characterization.

We may dispose of properties in transactions intended to qualify as like-kind exchanges under the Code. Such like-kind exchanges are intended to result in the deferral of gain for U.S. federal income tax purposes. The failure of any such transaction to qualify as a like-kind exchange could require us to pay federal income tax, possibly including the 100% prohibited transaction tax, depending on the facts and circumstances surrounding the particular transaction.

We may enter into hedging transactions, including with respect to foreign currency exchange rate and interest rate exposure on one or more of our assets or liabilities. Any such hedging transactions could take a variety of forms, including the use of derivative instruments such as swap contracts, cap or floor contracts, futures or forward contracts, and options. Income from a hedging transaction (including gain from the sale, disposition, or termination of a position in such a transaction) generally will not constitute gross income for purposes of the 75% and 95% gross income tests if we properly identify the transaction as specified in applicable Treasury regulations and we enter into such transaction (i) in the normal course of our business primarily to manage risk of interest rate changes or currency fluctuations with respect to borrowings made or to be made, or ordinary obligations incurred or to be incurred, to acquire or carry real estate assets; (ii) primarily to manage risk of currency fluctuations with respect to any item of income or gain that would be qualifying income under the 75% or 95% income tests; or (iii) in connection with the extinguishment of indebtedness with respect to which we have entered into a qualified hedging position described in clause (i) or the disposition of property with respect to which we have entered into a qualified hedging position described in clause (ii), primarily to manage the risks of such hedging positions. To the extent that we enter into other types of hedging transactions, the income from those transactions is likely to be treated as non-qualifying income for purposes of both the 75% and 95% gross income tests. Moreover, to the extent that a position in a hedging transaction has positive value at any particular point in time, it may be treated as an asset that does not qualify for purposes of the REIT asset tests. We intend to structure any hedging transactions in a manner that does not jeopardize our qualification as a REIT. We may conduct some or all of our hedging activities (including hedging activities relating to currency risk) through a TRS or other corporate entity, the income from which may be subject to U.S. federal income tax, rather than by participating in the arrangements directly or through pass-through subsidiaries. No assurance can be given, however, that our hedging activities will not give rise to income or assets that do not qualify for purposes of the REIT tests, or that our hedging activities will not adversely affect our ability to satisfy the REIT qualification requirements.

Foreclosure property is real property and any personal property incident to such real property (i) that we acquire as the result of having bid in the property at foreclosure, or having otherwise reduced the property to ownership or possession by agreement or process of law, after a default (or upon imminent default) on a lease of the property or a mortgage loan held by us and secured by the property, (ii) for which we acquired the related loan or lease at a time when default was not imminent or anticipated and (iii) with respect to which we made a proper election to treat the property as foreclosure property. We generally will be subject to tax at the maximum corporate rate (currently 35%) on any net income from foreclosure property, including any gain from the disposition of the foreclosure property, other than income that would otherwise be qualifying income for purposes of the 75% gross income test. Any gain from the sale of property for which a foreclosure property election

has been made will not be subject to the 100% tax on gains from prohibited transactions described above, even if the property would otherwise constitute inventory or dealer property. We do not anticipate receiving any income from foreclosure property that does not qualify for purposes of the 75% gross income test.

Any redetermined rents, redetermined deductions, excess interest, or redetermined TRS service income that we or our TRSs generate will be subject to a 100% penalty tax. In general, redetermined rents are rents from real property that are overstated as a result of any services furnished to any of our tenants by a TRS, redetermined deductions and excess interest represent any amounts that are deducted by a TRS for amounts paid to us that are in excess of the amounts that would have been deducted based on arm's length negotiations, and redetermined TRS service income is income of a TRS attributable to services provided to, or on behalf of, us (other than services furnished or rendered to a tenant of ours) to the extent such income is lower than the income the TRS would have earned based on arm's length negotiations. Rents that we receive will not constitute redetermined rents if they qualify for certain safe harbor provisions contained in the Code.

From time to time, our TRS may provide services to our tenants. We intend to set the fees paid to our TRS for such services at arm's length rates, although the fees paid may not satisfy the safe-harbor provisions described above. These determinations are inherently factual, and the IRS has broad discretion to assert that amounts paid between related parties should be reallocated to clearly reflect their respective incomes. If the IRS successfully made such an assertion, we would be required to pay a 100% penalty tax on the excess of an arm's length fee for tenant services over the amount actually paid.

If we fail to satisfy one or more requirements for REIT qualification other than the income or asset tests, we could avoid disqualification as a REIT if our failure is due to reasonable cause and not to willful neglect and we pay a penalty of $50,000 for each such failure. Relief provisions are also available for failures of the income tests and asset tests, as described above in "—Income Tests" and "—Asset Tests."

If we fail to qualify for taxation as a REIT in any taxable year, and the relief provisions described above do not apply, we would be subject to tax, including any applicable alternative minimum tax, on our taxable income at regular corporate rates. We cannot deduct distributions to stockholders in any year in which we are not a REIT, nor would we be required to make distributions in such a year. In this situation, to the extent of current and accumulated earnings and profits, distributions to stockholders would be taxable as regular corporate dividends. Such dividends paid to U.S. stockholders that are individuals, trusts and estates may be taxable at the preferential income tax rates for qualified dividends. In addition, subject to the limitations of the Code, corporate distributees may be eligible for the dividends received deduction. Unless we are entitled to relief under specific statutory provisions, we would also be disqualified from re-electing to be taxed as a REIT for the four taxable years following the year during which we lost our qualification. It is not possible to state whether, in all circumstances, we would be entitled to this statutory relief.

General. All of our investments will be held through our operating partnership, which, as noted above, is currently treated as a disregarded entity for U.S. federal income tax purposes. In addition, our operating partnership holds certain of its investments indirectly through subsidiary entities that are

treated as partnerships or disregarded entities for U.S. federal income tax purposes. In general, entities that are treated as partnerships or disregarded entities for U.S. federal income tax purposes are "pass-through" entities which are generally not required to pay federal income tax. Rather, partners or members of such entities are allocated their shares of the items of income, gain, loss, deduction and credit of the partnership or limited liability company, and are potentially required to pay tax (or, if the partner or member is a REIT, it would be subject to a distribution requirement) on this income, without regard to whether they receive a distribution from the partnership or limited liability company. We will include in our income our share of these partnership and limited liability company items for purposes of the various gross income tests, the computation of our REIT taxable income, and the REIT distribution requirements. Moreover, for purposes of the asset tests, we will include our pro rata share of assets held through our operating partnership and the subsidiary partnerships and limited liability companies, based on our capital interest in each such entity. See "—Taxation of CyrusOne Inc."

Entity Classification. Our interests in our operating partnership and the subsidiary partnerships and limited liability companies involve special tax considerations, including the possibility that the IRS might challenge the status of these entities as partnerships or disregarded entities (as applicable), as opposed to associations taxable as corporations for U.S. federal income tax purposes. If our operating partnership or a subsidiary partnership or limited liability company were treated as an association, it would be taxable as a corporation and would be required to pay an entity-level tax on its income. In this situation, the character of our assets and items of gross income would change and could prevent us from satisfying the REIT asset tests and possibly the REIT income tests. See "—Taxation of CyrusOne Inc.—Asset Tests" and "—Income Tests." This, in turn, could prevent us from qualifying as a REIT. See "—Failure to Qualify" for a discussion of the effect of our failure to meet these tests. In addition, a change in the tax status of our operating partnership, a subsidiary partnership or limited liability company might be treated as a taxable event. If so, we might incur a distribution requirement without a corresponding receipt of cash. We believe that our operating partnership and each of our other partnerships and limited liability companies will be classified as partnerships or disregarded entities for U.S. federal income tax purposes.

Allocations of Income, Gain, Loss and Deduction. A partnership agreement (or, in the case of a limited liability company treated as a partnership for U.S. federal income tax purposes, the limited liability company agreement) will generally determine the allocation of partnership income and loss among partners. Generally, Section 704(b) of the Code and the Treasury regulations thereunder require that partnership allocations respect the economic arrangement of the partners. If an allocation of partnership income or loss does not comply with the requirements of Section 704(b) of the Code and the Treasury regulations thereunder, the item subject to the allocation will be reallocated in accordance with the partners' interests in the partnership. This reallocation will be determined by taking into account all of the facts and circumstances relating to the economic arrangement of the partners with respect to such item. In the event that our operating partnership becomes a partnership (rather than a disregarded entity) for U.S. federal income tax purposes, we intend that any allocations of taxable income and loss will comply with the requirements of Section 704(b) of the Code and the Treasury regulations thereunder.

Tax Allocations with Respect to the Properties. Under Section 704(c) of the Code, income, gain, loss and deduction attributable to appreciated or depreciated property that is contributed to a partnership (including a limited liability company treated as a partnership for U.S. federal income tax purposes) in exchange for an interest in the partnership, must be allocated in a manner so that the contributing partner is charged with the unrealized gain or benefits from the unrealized loss associated with the property at the time of the contribution, as adjusted from time to time. The amount of the unrealized gain or unrealized loss generally is equal to the difference between the fair market value or book value and the adjusted tax basis of the contributed property at the time of contribution (this

difference is referred to as a book-tax difference), as adjusted from time to time. These allocations are solely for U.S. federal income tax purposes and do not affect the book capital accounts or other economic or legal arrangements among the partners. In the event that our operating partnership becomes a partnership (rather than a disregarded entity) for U.S. federal income tax purposes, we intend that any allocations will be made in a manner consistent with Section 704(c) of the Code and the Treasury regulations thereunder.

Any property acquired by a partnership in which we invest in a taxable transaction will initially have a tax basis equal to its fair market value, and Section 704(c) of the Code will not apply.

New Partnership Audit Rules. The Bipartisan Budget Act of 2015 changes the rules applicable to U.S. federal income tax audits of partnerships. Under the new rules, among other changes and subject to certain exceptions, any audit adjustment to items of income, gain, loss, deduction or credit of a partnership (and any partner's distributive share thereof) is determined, and taxes, interest or penalties attributable thereto are assessed and collected, at the partnership level. Although certain aspects of these new rules remain uncertain, it is possible that they could result in partnerships in which we directly or indirectly invest being required to pay additional taxes, interest and penalties as a result of an audit adjustment, and we, as a direct or indirect partner of these partnerships, could be required to bear the economic burden of those taxes, interest and penalties even though we, as a REIT, may not otherwise have been required to pay additional corporate-level taxes as a result of the related audit adjustment.

The following is a summary of certain U.S. federal income tax consequences of the ownership and disposition of our stock applicable to taxable U.S. stockholders. A "U.S. stockholder" is a beneficial owner of our common stock that is, for U.S. federal income tax purposes:

If a partnership, including for this purpose any entity that is treated as a partnership for U.S. federal income tax purposes, holds our common stock, the tax treatment of a partner in the partnership will generally depend upon the status of the partner and the activities of the partnership. An investor that is a partnership and the partners in such partnership should consult their tax advisors about the U.S. federal income tax consequences of the acquisition, ownership and disposition of our common stock.

Distributions. So long as we qualify as a REIT, the distributions that we make to our taxable U.S. stockholders out of current or accumulated earnings and profits that we do not designate as capital gain dividends will generally be taken into account by such stockholders as ordinary income and will not be eligible for the dividends received deduction for corporations. With limited exceptions, our dividends are not eligible for taxation at the preferential income tax rates for qualified dividends

received by most U.S. stockholders that are individuals, trusts and estates from taxable C corporations. Such stockholders, however, are taxed at the preferential rates on dividends designated by and received from REITs to the extent that the dividends are attributable to:

In addition, for taxable years that begin after December 31, 2017 and before January 1, 2026, U.S. stockholders that are individuals, trusts or estates are generally entitled to a deduction equal to 20% of the aggregate amount of ordinary income dividends received from a REIT (not including capital gain dividends or dividends eligible for the preferential rates applicable to qualified dividends as described above), subject to certain limitations. Under final regulations recently issued by the Internal Revenue Service, in order to qualify for this deduction with respect to a dividend on our common shares, a stockholder must hold such shares for more than 45 days during the 91-day period beginning on the date which is 45 days before the date on which such shares become ex-dividend with respect to such dividend (taking into account certain special holding period rules that may, among other consequences, reduce a shareholder's holding period during any period in which the shareholder has diminished its risk of loss with respect to the shares). Stockholders are urged to consult their tax advisors as to their ability to claim this deduction.

Distributions that we designate as capital gain dividends will generally be taxed to our U.S. stockholders as long-term capital gains, to the extent that such distributions do not exceed our actual net capital gain for the taxable year, without regard to the period for which the stockholder that receives such distribution has held its stock. We may elect to retain and pay taxes on some or all of our net long-term capital gains, in which case we may elect to treat our U.S. stockholders as having received, solely for tax purposes, our undistributed capital gains, and the stockholders as receiving a corresponding credit for taxes that we paid on such undistributed capital gains. See "Taxation of CyrusOne Inc.—Annual Distribution Requirements." Corporate stockholders may be required to treat up to 20% of some capital gain dividends as ordinary income. Long-term capital gains are generally taxable at reduced maximum U.S. federal rates in the case of U.S. stockholders that are individuals, trusts or estates, and ordinary income rates in the case of U.S. stockholders that are corporations. Capital gains attributable to the sale of depreciable real property held for more than 12 months are subject to a 25% maximum U.S. federal income tax rate for taxpayers who are taxed as individuals, to the extent of previously claimed depreciation deductions.

Distributions in excess of our current and accumulated earnings and profits will generally represent a return of capital and will not be taxable to a stockholder to the extent that the amount of such distributions does not exceed the adjusted basis of the stockholder's shares in respect of which the distributions were made. Rather, the distribution will reduce the adjusted basis of the stockholder's shares. To the extent that such distributions exceed the adjusted basis of a stockholder's shares, the stockholder generally must include such distributions in income as long-term capital gain if the shares have been held for more than one year, or short-term capital gain if the shares have been held for one year or less. In addition, any dividend that we declare in October, November or December of any year and that is payable to a stockholder of record on a specified date in any such month will be treated as

both paid by us and received by the stockholder on December 31 of such year, provided that we actually pay the dividend before the end of January of the following calendar year.

To the extent that we have available net operating losses and capital losses carried forward from prior tax years, such losses may, subject to limitations, reduce the amount of distributions that we must make in order to comply with the REIT distribution requirements. See "Taxation of CyrusOne Inc.—Annual Distribution Requirements." Such losses, however, are not passed through to stockholders and do not offset income of stockholders from other sources, nor would such losses affect the character of any distributions that we make, which are generally subject to tax in the hands of stockholders to the extent that we have current or accumulated earnings and profits.

Dispositions of Our Stock. If a U.S. stockholder sells or disposes of shares of our stock, the stockholder will generally recognize gain or loss for U.S. federal income tax purposes in an amount equal to the difference between the amount of cash and the fair market value of any property received on the sale or other disposition and the stockholder's adjusted tax basis in the shares of stock. In general, capital gains recognized by individuals, trusts and estates upon the sale or disposition of our stock will be subject to a reduced maximum U.S. federal income tax rate if the stock is held for more than one year, and will be taxed at ordinary income rates if the stock is held for one year or less. Gains recognized by stockholders that are corporations are subject to U.S. federal income tax at ordinary income rates, whether or not such gains are classified as longterm capital gains. Capital losses recognized by a stockholder upon the disposition of our stock that was held for more than one year at the time of disposition will be considered long-term capital losses, and are generally available only to offset capital gain income of the stockholder but not ordinary income (except in the case of individuals, who may also offset up to $3,000 of ordinary income each year). In addition, any loss upon a sale or exchange of shares of our stock by a stockholder who has held the shares for six months or less, after applying holding period rules, will be treated as a long-term capital loss to the extent of actual or deemed distributions that we make that are required to be treated by the stockholder as long-term capital gain.

If an investor recognizes a loss upon a subsequent disposition of our stock or other securities in an amount that exceeds a prescribed threshold, it is possible that the provisions of Treasury regulations involving "reportable transactions" could apply, with a resulting requirement to separately disclose the loss-generating transaction to the IRS. These regulations, though directed towards "tax shelters," are broadly written and apply to transactions that would not typically be considered tax shelters. The Code imposes significant penalties for failure to comply with these requirements. You should consult your tax advisor concerning any possible disclosure obligation with respect to the receipt or disposition of our stock or securities or transactions that we might undertake directly or indirectly. Moreover, you should be aware that we and other participants in the transactions in which we are involved (including their advisors) might be subject to disclosure or other requirements pursuant to these regulations.

Passive Activity Losses and Investment Interest Limitations. Distributions that we make and gains arising from the sale or exchange by a U.S. stockholder of our stock will not be treated as passive activity income. As a result, stockholders will not be able to apply any "passive losses" against income or gain relating to our stock. To the extent that distributions we make do not constitute a return of capital, they will be treated as investment income for purposes of computing the investment interest limitation.

The following is a summary of certain U.S. federal income and estate tax consequences of the ownership and disposition of our stock applicable to non-U.S. stockholders. A "non-U.S. stockholder" is a beneficial owner of our common stock other than a partnership or U.S. stockholder.

Ordinary Dividends. The portion of dividends received by non-U.S. stockholders that (i) is payable out of our earnings and profits, (ii) is not attributable to capital gains that we recognize and (iii) is not effectively connected with a U.S. trade or business of the non-U.S. stockholder, will be subject to U.S. withholding tax at the rate of 30%, unless reduced or eliminated by treaty.

In general, non-U.S. stockholders will not be considered to be engaged in a U.S. trade or business solely as a result of their ownership of our stock. In cases where the dividend income from a non-U.S. stockholder's investment in our stock is, or is treated as, effectively connected with the non-U.S. stockholder's conduct of a U.S. trade or business, the non-U.S. stockholder generally will be subject to U.S. federal income tax at graduated rates, in the same manner as U.S. stockholders are taxed with respect to such dividends. Such effectively connected income must generally be reported on a U.S. income tax return filed by or on behalf of the non-U.S. stockholder. The income may also be subject to a branch profits tax at the rate of 30% (unless reduced or eliminated by treaty) in the case of a non-U.S. stockholder that is a corporation.

Non-Dividend Distributions. Unless our stock constitutes a U.S. real property interest ("USRPI"), distributions that we make which are not dividends out of our earnings and profits will not be subject to U.S. income tax. If we cannot determine at the time a distribution is made whether or not the distribution will exceed current and accumulated earnings and profits, the distribution will be subject to withholding at the rate applicable to dividends. The non-U.S. stockholder may seek a refund from the IRS of any amounts withheld if it is subsequently determined that the distribution was, in fact, in excess of our current and accumulated earnings and profits. If our stock constitutes a USRPI, as described below, distributions that we make in excess of the sum of (i) the stockholder's proportionate share of our earnings and profits, plus (ii) the stockholder's basis in its stock, will be taxed under the Foreign Investment in Real Property Tax Act of 1980 ("FIRPTA"), at the rate of tax, including any applicable capital gains rates, that would apply to a U.S. stockholder of the same type (e.g., an individual or a corporation, as the case may be), and the collection of the tax may be enforced by a withholding at a rate of 15% of the amount by which the distribution exceeds the stockholder's share of our earnings and profits.

Capital Gain Dividends. Under FIRPTA, a distribution that we make to a non-U.S. stockholder, to the extent attributable to gains from dispositions of USRPIs that we held directly or through pass-through subsidiaries, or USRPI capital gains, will, except as described below, be considered effectively connected with a U.S. trade or business of the non-U.S. stockholder and will be subject to U.S. income tax at the rates applicable to U.S. individuals or corporations, without regard to whether we designate the distribution as a capital gain dividend. See above under "—Taxation of Non-U.S. Stockholders—Ordinary Dividends," for a discussion of the consequences of income that is effectively connected with a U.S. trade or business. In addition, we will be required to withhold tax equal to the highest corporate tax rate applied to the maximum amount that could have been designated as USRPI capital gain dividends. Distributions subject to FIRPTA may also be subject to a branch profits tax at the rate of 30% (unless reduced or eliminated by treaty) in the hands of a non-U.S. stockholder that is a corporation. A distribution is not attributable to USRPI capital gain if we held an interest in the underlying asset solely as a creditor. Capital gain dividends received by a non-U.S. stockholder that are attributable to dispositions of our assets other than USRPIs are not subject to U.S. federal income or withholding tax, unless (i) the gain is effectively connected with the non-U.S. stockholder's U.S. trade or business, in which case the non-U.S. stockholder would be subject to the same treatment as U.S. stockholders with respect to such gain, except that a non-U.S. stockholder that is a corporation may also be subject to a branch profits tax at the rate of 30% (unless reduced or eliminated by treaty), or (ii) the non-U.S. stockholder is a nonresident alien individual who was present in the United States for 183 days or more during the taxable year and certain other requirements are met, in which case the non-U.S. stockholder will incur a 30% tax on his capital gains. A significant portion of our assets are USRPIs.

A capital gain dividend that would otherwise have been treated as a USRPI capital gain will not be so treated or be subject to FIRPTA, and generally will not be treated as income that is effectively connected with a U.S. trade or business, and instead will be treated in the same manner as an ordinary dividend (see "—Taxation of Non-U.S. Stockholders—Ordinary Dividends"), if (i) the capital gain dividend is received with respect to a class of stock that is regularly traded on an established securities market located in the United States and (ii) the recipient non-U.S. stockholder does not own more than 10% of that class of stock at any time during the year ending on the date on which the capital gain dividend is received. Our common stock is, and we anticipate that it will continue to be, "regularly traded" on an established securities exchange.

Dispositions of Our Stock. Unless our stock constitutes a USRPI, a sale of our stock by a non-U.S. stockholder generally will not be subject to U.S. taxation. Subject to certain exceptions discussed below, our stock will be treated as a USRPI if, at any time during a prescribed testing period, 50% or more of our assets consist of interests in real property located within the United States, excluding, for this purpose, interests in real property solely in a capacity as a creditor. We believe that 50% or more of our assets consists of USRPIs.

Even if the foregoing 50% test is met, however, our stock will not constitute a USRPI if we are a "domestically controlled qualified investment entity." A domestically controlled qualified investment entity includes a REIT, less than 50% of the value of which is held, directly or indirectly, by non-U.S. stockholders at all times during a specified testing period (after applying certain presumptions regarding the ownership of our stock, as described in Section 897(h)(4)(E) of the Code). As described above, our charter contains restrictions designed to protect our status as a "domestically controlled qualified investment entity," and we believe that we are and will remain a domestically controlled qualified investment entity, and that a sale of our stock should not be subject to taxation under FIRPTA. However, no assurance can be given that we are or will remain a domestically controlled qualified investment entity.

In the event that we are not a domestically controlled qualified investment entity, but our stock is "regularly traded," as defined by applicable Treasury regulations, on an established securities market, a non-U.S. stockholder's sale of our common stock nonetheless also would not be subject to tax under FIRPTA as a sale of a USRPI, provided that the selling non-U.S. stockholder held 10% or less of our outstanding shares of our common stock any time during a prescribed testing period. Our common stock is, and we expect that it will continue to be, regularly traded on an established securities market.

If gain on the sale of our stock were subject to taxation under FIRPTA, the non-U.S. stockholder would be required to file a U.S. federal income tax return and would be subject to the same treatment as a U.S. stockholder with respect to such gain, subject to applicable alternative minimum tax and a special alternative minimum tax in the case of non-resident alien individuals. Moreover, in order to enforce the collection of the tax, the purchaser of the stock could be required to withhold 15% of the purchase price and remit such amount to the IRS.

Gain from the sale of our stock that would not otherwise be subject to FIRPTA will nonetheless be taxable in the United States to a non-U.S. stockholder in two cases: (i) if the non-U.S. stockholder's investment in our stock is effectively connected with a U.S. trade or business conducted by such non-U.S. stockholder, the non-U.S. stockholder will be subject to the same treatment as a U.S. stockholder with respect to such gain, except that a non-U.S. stockholder that is a corporation may also be subject to a branch profits tax at a rate of 30% (unless reduced or eliminated by treaty), or (ii) if the non-U.S. stockholder is a nonresident alien individual who was present in the United States for 183 days or more during the taxable year and certain other requirements are met, the nonresident alien individual will be subject to a 30% tax on the individual's capital gain. In addition, even if we are a domestically controlled qualified investment entity, upon disposition of our stock, a non-U.S. stockholder may be treated as having gain from the sale or exchange of a USRPI if the non-U.S.

stockholder (a) disposes of our common stock within a 30-day period preceding the ex-dividend date of a distribution, any portion of which, but for the disposition, would have been treated as gain from the sale or exchange of a USRPI and (b) acquires, or enters into a contract or option to acquire, other shares of our common stock within 30 days after such ex-dividend date.

Special FIRPTA Rules. Certain provisions under FIRPTA create certain exemptions from FIRPTA and otherwise modify the application of the foregoing FIRPTA rules for particular types of non-U.S. investors, including "qualified foreign pension funds" and their wholly owned foreign subsidiaries and certain widely held, publicly traded "qualified collective investment vehicles." Non-U.S. stockholders are urged to consult their own tax advisors regarding the applicability of these or any other special FIRPTA rules to their particular investment in our common stock.

Estate Tax. If our stock is owned or treated as owned by an individual who is not a citizen or resident (as specially defined for U.S. federal estate tax purposes) of the United States at the time of such individual's death, the stock will be includable in the individual's gross estate for U.S. federal estate tax purposes, unless an applicable estate tax treaty provides otherwise, and may therefore be subject to U.S. federal estate tax.

Non-U.S. stockholders are urged to consult their tax advisors regarding the U.S. federal, state, local and foreign income and other tax consequences of owning and disposing of our stock.

Tax-exempt entities, including qualified employee pension and profit sharing trusts and individual retirement accounts, generally are exempt from U.S. federal income taxation. However, they may be subject to taxation on their unrelated business taxable income ("UBTI"). While some investments in real estate may generate UBTI, the IRS has ruled that dividend distributions from a REIT to a tax-exempt entity do not constitute UBTI. Based on that ruling, and provided that (i) a tax-exempt stockholder has not held our stock as "debt financed property" within the meaning of the Code (i.e., where the acquisition or holding of the property is financed through a borrowing by the tax-exempt stockholder) and (ii) our stock is not otherwise used in an unrelated trade or business, distributions that we make and income from the sale of our stock generally should not give rise to UBTI to a tax-exempt stockholder.

Tax-exempt stockholders that are social clubs, voluntary employee benefit associations, supplemental unemployment benefit trusts, and qualified group legal services plans exempt from U.S. federal income taxation under Sections 501(c)(7), (c)(9), (c)(17) and (c)(20) of the Code are subject to different UBTI rules, which generally require such stockholders to characterize distributions that we make as UBTI.

In certain circumstances, a pension trust that owns more than 10% of our stock could be required to treat a percentage of any dividends received from us as UBTI if we are a "pension-held REIT." We will not be a pension-held REIT unless (i) we are required to "look through" one or more of our pension trust stockholders in order to satisfy the REIT "closely held" test and (ii) either (a) one pension trust owns more than 25% of the value of our stock or (b) one or more pension trusts, each individually holding more than 10% of the value of our stock, collectively own more than 50% of the value of our stock. Certain restrictions on ownership and transfer of our stock generally should prevent a tax-exempt entity from owning more than 10% of the value of our stock and generally should prevent us from becoming a pension-held REIT.

Tax-exempt stockholders are urged to consult their tax advisors regarding the U.S. federal, state, local and foreign income and other tax consequences of owning and disposing of our stock.

The present U.S. federal income tax treatment of REITs may be modified, possibly with retroactive effect, by legislative, judicial or administrative action at any time. The REIT rules are constantly under review by persons involved in the legislative process and by the IRS and the Treasury, which may result in statutory changes as well as revisions to regulations and interpretations. For example, the "Tax Cuts and Jobs Act" (the "Act") significantly changed the U.S. federal income tax laws applicable to businesses and their owners, including REITs and their shareholders. We cannot predict the long-term effect of the Act or any future law changes on REITs or their shareholders. Changes to the U.S. federal tax laws and interpretations thereof could adversely affect an investment in our common stock.

Certain U.S. stockholders who are individuals, estates or trusts and whose income exceeds certain thresholds are required to pay a 3.8% Medicare tax on dividends and certain other investment income, including capital gains from the sale or other disposition of our common stock.

Sections 1471 to 1474 of the Code and existing guidance issued thereunder require withholding at a rate of 30% on dividends in respect of our common stock held by or through certain foreign financial institutions (including investment funds), unless such institution enters into an agreement with the Treasury to report, on an annual basis, information with respect to shares in the institution held by certain U.S. persons and by certain non-U.S. entities that are wholly or partially owned by U.S. persons and to withhold on certain payments. Accordingly, the entity through which our common stock is held will affect the determination of whether such withholding is required. Similarly, dividends in respect of our common stock held by an investor that is a non-financial non-U.S. entity which does not qualify under certain exemptions will be subject to withholding at a rate of 30%, unless such entity either (i) certifies that such entity does not have any "substantial United States owners" or (ii) provides certain information regarding the entity's "substantial United States owners," which we or the applicable withholding agent will in turn provide to the Secretary of the Treasury. An intergovernmental agreement between the United States and an applicable foreign country, or future Treasury regulations or other guidance, may modify these requirements. We will not pay any additional amounts to stockholders in respect of any amounts withheld. Non-U.S. stockholders are encouraged to consult their tax advisors regarding the possible implications of these rules on their investment in our common stock.

We and our subsidiaries and stockholders may be subject to state, local or foreign taxation in various jurisdictions including those in which we or they transact business, own property or reside. Our state, local or foreign tax treatment and that of our stockholders may not conform to the U.S. federal income tax treatment discussed above. Any foreign taxes that we incur do not pass through to stockholders as a credit against their U.S. federal income tax liability. Prospective investors should consult their tax advisors regarding the application and effect of state, local and foreign income and other tax laws on an investment in our stock.

We and any selling securityholder may sell the securities under this prospectus in one or more of the following ways (or in any combination) from time to time:

In addition, we and any selling securityholder may sell any securities covered by this prospectus in private transactions, and any selling securityholder may sell under Rule 144 of the Securities Act, rather than pursuant to this prospectus.

If underwriters or dealers are used in the sale, the securities will be acquired by the underwriters or dealers for their own account and may be resold from time to time in one or more transactions, including:

As applicable, we and our underwriters, dealers or agents, reserve the right to accept or reject all or part of any proposed purchase of the securities. We will set forth in a prospectus supplement the terms and offering of securities by us or any selling securityholder, including:

We or any selling securityholder may enter into derivative transactions with third parties or sell securities not covered by this prospectus to third parties in privately negotiated transactions from time to time. If the applicable prospectus supplement indicates, in connection with those derivative transactions, such third parties (or affiliates of such third parties) may sell securities covered by this

prospectus and the applicable prospectus supplement, including in short sale transactions. If so, such third parties (or affiliates of such third parties) may use securities pledged by us or any selling securityholder or borrowed from us or any securityholder or others to settle those sales or to close out any related open borrowings of securities, and may use securities received from us or any selling securityholder in settlement of those derivative transactions to close out any related open borrowings of securities. The third parties (or affiliates of such third parties) in such sale transactions by us or any selling securityholder will be underwriters and will be identified in an applicable prospectus supplement (or a post-effective amendment). We may also sell securities under this prospectus upon the exercise of rights that may be issued to our securityholders.

We or any selling securityholder may loan or pledge securities to a financial institution or other third party that in turn may sell the securities using this prospectus and an applicable prospectus supplement. Such financial institution or third party may transfer its economic short position to investors in our securities or in connection with a simultaneous offering of other securities offered by this prospectus.

If underwriters are used in the sale of our securities, the securities will be acquired by the underwriters for their own account and may be resold from time to time in one or more transactions described above. The securities may be offered to the public either through underwriting syndicates represented by managing underwriters or directly by underwriters. Generally, the underwriters' obligations to purchase the securities will be subject to conditions precedent and the underwriters will be obligated to purchase all of the securities if they purchase any of the securities. We may use underwriters with which we have a material relationship and will describe in the prospectus supplement, naming the underwriter, the nature of any such relationship.

We or any selling securityholder may sell the securities through agents from time to time. When we or any selling securityholder sell securities through agents, the prospectus supplement will name any agent involved in the offer or sale of securities and any commissions we or any selling securityholder pay to them. Generally, any agent will be acting on a best efforts basis for the period of its appointment.

We or any selling securityholder may authorize underwriters, dealers or agents to solicit offers by certain purchasers to purchase our securities from us or any selling securityholder at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. The contracts will be subject only to those conditions set forth in the prospectus supplement, and the prospectus supplement will set forth any commissions we or any selling securityholder pay for solicitation of these contracts.

Underwriters, dealers and agents may contract for or otherwise be entitled to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments made by the underwriters, dealers or agents, under agreements between us or any selling securityholders and the underwriters, dealers and agents.

We or any selling securityholder may grant underwriters who participate in the distribution of our securities an option to purchase additional securities to cover over-allotments, if any, in connection with the distribution.

Underwriters, dealers or agents may receive compensation in the form of discounts, concessions or commissions from us, any selling securityholders or our purchasers, as their agents in connection with the sale of our securities. These underwriters, dealers or agents may be considered to be underwriters under the Securities Act. As a result, discounts, commissions or profits on resale received by the underwriters, dealers or agents may be treated as underwriting discounts and commissions. The

prospectus supplement for any securities offered by us or any selling securityholders will identify any such underwriter, dealer or agent and describe any compensation received by them from us. Any public offering price and any discounts or concessions allowed or re-allowed or paid to dealers may be changed from time to time.

Any underwriter may engage in over-allotment transactions, stabilizing transactions, short-covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Over-allotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short-covering transactions involve purchases of our securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time. We make no representation or prediction as to the direction or magnitude of any effect these transactions may have on the price of our securities. For a description of these activities, see the information under the heading "Underwriting" in the applicable prospectus supplement.

Underwriters, broker-dealers or agents who may become involved in the sale of our securities may engage in transactions with and perform other services for us for which they receive compensation.

In connection with an offering through underwriters, an underwriter may, to the extent permitted by applicable rules and regulations, purchase and sell securities in the open market. These transactions, to the extent permitted by applicable rules and regulations, may include short sales, stabilizing transactions and purchases to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater number of securities than they are required to purchase in the offering. "Covered" short sales are sales made in an amount not greater than the underwriters' option to purchase additional securities from us in the offering, if any. If the underwriters have an over-allotment option to purchase additional securities from us, the underwriters may consider, among other things, the price of securities available for purchase in the open market as compared to the price at which they may purchase securities through the over-allotment option. "Naked" short sales, which may be prohibited or restricted by applicable rules and regulations, are any sales in excess of such option or where the underwriters do not have an over-allotment option. The underwriters must close out any naked short position by purchasing securities in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the securities in the open market after pricing that could adversely affect investors who purchase in the offering.

Accordingly, to cover these short sales positions or to otherwise stabilize or maintain the price of the securities, the underwriters may bid for or purchase securities in the open market and may impose penalty bids. If penalty bids are imposed, selling concessions allowed to syndicate members or other broker-dealers participating in the offering are reclaimed if securities previously distributed in the offering are repurchased, whether in connection with stabilization transactions or otherwise. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. The imposition of a penalty bid may also affect the price of the securities to the extent that it discourages resale of the securities. The magnitude or effect of any stabilization or other transactions is uncertain.

We or any selling securityholder may also sell securities directly to one or more purchasers without using underwriters or agents. In this case, no agents, underwriters or dealers would be involved. We may sell securities upon the exercise of rights that we may issue to our securityholders. We or any selling securityholder may also sell securities directly to institutional investors or others who may be deemed to be underwriters within the meaning of the Securities Act with respect to any sale of those securities.

To the extent that we make sales through one or more underwriters or agents in at-the-market offerings, we will do so pursuant to the terms of a sales agency financing agreement or other at-the-market offering arrangement between us and the underwriters or agents. If we engage in at-the-market sales pursuant to any such agreement, we will issue and sell our securities through one or more underwriters or agents, which may act on an agency basis or on a principal basis. During the term of any such agreement, we may sell securities on a daily basis in exchange transactions or otherwise as we agree with the underwriters or agents. The agreement will provide that any securities sold will be sold at prices related to the then prevailing market prices for our securities. Therefore, exact figures regarding proceeds that will be raised or commissions to be paid cannot be determined at this time. Pursuant to the terms of the agreement, we may agree to sell, and the relevant underwriters or agents may agree to solicit offers to purchase, blocks of our common stock or other securities. The terms of each such agreement will be set forth in more detail in a prospectus supplement to this prospectus.

Any common stock sold pursuant to a prospectus supplement will be listed on the NASDAQ Global Select Market. The securities other than common stock may or may not be listed on a national securities exchange. It is possible that one or more underwriters may make a market in a class or series of securities, but the underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We cannot give any assurance as to the liquidity of the trading market for any of the securities.

Unless otherwise indicated in the prospectus supplement, certain legal matters regarding the validity of the securities offered hereby will be passed upon for us by Cravath, Swaine & Moore LLP and by Venable LLP, with respect to matters of Maryland law. Certain U.S. federal income tax matters will be passed upon for us by Skadden, Arps, Slate, Meagher & Flom LLP.

The consolidated financial statements, and the related financial statement schedules, incorporated in this prospectus by reference from CyrusOne Inc.'s Annual Report on Form 10-K, and the effectiveness of CyrusOne Inc.'s internal control over financial reporting, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports, which are incorporated herein by reference. Such consolidated financial statements and financial statement schedules have been so incorporated in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing.

The audited historical financial statements of Zenium Topco Limited for the fiscal year ended December 31, 2017 included in exhibit 99.1 of CyrusOne Inc.'s Current Report on Form 8-K/A filed November 1, 2018 (as amended by the Form 8-K/A filed April 23, 2019) have been so incorporated by reference in reliance on the report (which contains an explanatory paragraph relating to the exclusion of Zenium Topco Limited's comparative financial information as described in Note 2.1 to the financial statements) of PricewaterhouseCoopers LLP, independent auditors, given on the authority of said firm as experts in auditing and accounting.

Title of Each Class of Securities to be Registered	Proposed Maximum Aggregate Offering Price	Amount of Registration Fee(1)(2)




Common Stock, par value $0.01 per share	$750,000,000	$81,825


J.P. MORGAN	BARCLAYS	BMO CAPITAL MARKETS
CREDIT AGRICOLE CIB	DEUTSCHE BANK SECURITIES	FIFTH THIRD SECURITIES
GOLDMAN SACHS & CO. LLC	JEFFERIES	KEYBANC CAPITAL MARKETS
MORGAN STANLEY	MUFG	RBC CAPITAL MARKETS
STIFEL	TD SECURITIES	TRUIST SECURITIES


ABOUT THIS PROSPECTUS SUPPLEMENT			S-iii
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS			S-iv
WHERE YOU CAN FIND MORE INFORMATION			S-vi
INCORPORATION BY REFERENCE			S-vii
SUMMARY			S-1
RISK FACTORS			S-4
USE OF PROCEEDS			S-10
PLAN OF DISTRIBUTION			S-12
LEGAL MATTERS			S-19
EXPERTS			S-20


J.P. MORGAN	BARCLAYS	BMO CAPITAL MARKETS
CREDIT AGRICOLE CIB	DEUTSCHE BANK SECURITIES	FIFTH THIRD SECURITIES
GOLDMAN SACHS & CO. LLC	JEFFERIES	KEYBANC CAPITAL MARKETS
MORGAN STANLEY	MUFG	RBC CAPITAL MARKETS
STIFEL	TD SECURITIES	TRUIST SECURITIES


Special Note Regarding Forward-Looking Statements		1
About This Prospectus		3
Where You Can Find More Information		3
Incorporation By Reference		4
Our Company		5
Risk Factors		5
Selling Securityholders		5
Use of Proceeds		5
Description of Debt Securities		7
Description of CyrusOne Inc. Common Stock		16
Description of CyrusOne Inc. Preferred Stock		18
Description of Warrants		21
Description of Rights		24
Description of Units		25
Restrictions on Ownership and Transfer		26
Description of the Partnership Agreement of CyrusOne LP		30
Certain Provisions of Maryland Law and of Our Charter and Bylaws		39
U.S. Federal Income Tax Considerations		45
Plan of Distribution		67
Legal Matters		71
Experts		72