DIGITAL REALTY TRUST, INC. files 424B7: prospectus (424B)

The information in this preliminary prospectus supplement relates to an effective registration statement under the Securities Act of

1933, as amended, but is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and neither we nor the selling stockholders are soliciting offers to buy these securities in any state or other jurisdiction where the offer or sale is not permitted.

Subject to completion Preliminary Prospectus Supplement dated June 29, 2026

PROSPECTUS SUPPLEMENT (To Prospectus dated

$2,346,087,437.83 Digital Realty Trust, Inc.

Common Stock

The selling stockholders identified in this prospectus supplement are selling $2,346,087,437.83 of shares of our common stock, $0.01 par value per share (“common stock”), in this offering. We are not selling any shares of common stock under this prospectus supplement and will not receive any proceeds from the sale of shares by the selling stockholders. See “Use of Proceeds.”

We are organized and conduct our operations to qualify as a real estate investment trust (“REIT”), for U.S. federal income tax purposes. To assist us in complying with certain federal income tax requirements applicable to REITs, our charter contains certain restrictions relating to the ownership and transfer of our stock, including an ownership limit of 9.8% (by value or by number of shares, whichever is more restrictive) on the outstanding shares of our common stock.

Our common stock is listed on the New York Stock Exchange under the symbol “DLR”. The last reported sale price of our common stock on the New York Stock Exchange on June 26, 2026 was $193.00 per share.

Investing in our common stock involves risks. See “ Risk Factors ” beginning on page S-5 of this prospectus supplement and the matters discussed in the documents incorporated by reference in this prospectus supplement and the accompanying prospectus.

Neither the U.S. Securities and Exchange Commission (the “SEC”) nor any state securities commission, nor any other regulatory body has approved

Per share Total Public offering price $ $

Underwriting discounts and commissions $ $

Proceeds, before expenses, to the selling stockholders $ $

(1) Please see the section entitled “Underwriting” for a description of the compensation payable to the underwriter.

The underwriter expects to deliver the shares to purchasers on or about , 2026 through the book-entry facilities of The Depository Trust Company.

Name of Selling Stockholder Number Percentage Number Percentage

Blackstone — —

* less than 1%

(2) Reflects $947,855,214.04 of shares to be held directly by BIP US Nucleus Aggregator L.P., $947,844,000.71 of shares to be held directly by BREP US Nucleus Aggregator L.P., $74,744,380.55 of shares to be held directly by BXPE Nucleus US Holdco L.P., $6,623,015.61 of shares to be held directly by BXPE Nucleus Lux Holdco L.P. and $369,020,826.92 of shares to be held directly by BTO Nucleus Holdings DE L.P. The number of shares offered by each of the foregoing selling stockholders will be determined by dividing such dollar amounts by the closing price per share of our common stock on the New York Stock Exchange on June 29, 2026, rounded down to the nearest whole number.

The general partner of BIP US Nucleus Aggregator, L.P. is

Blackstone Infrastructure Associates Non-ECI L.P. The general partner of Blackstone Infrastructure Associates Non-ECI L.P. is BIA GP L.P. The general partner of BIA GP

L.P. is BIA GP L.L.C. The sole member of BIA GP L.L.C. is Blackstone Holdings III L.P. The general partner of Blackstone Holdings III L.P. is Blackstone Holdings III GP Management L.L.C.

The general partner of BREP US Nucleus Aggregator L.P. is BREP US Nucleus Aggregator GP LLC. Blackstone Real Estate Associates X L.P. is the managing member of BREP US Nucleus Aggregator GP LLC. The general partner of Blackstone Real Estate Associates X L.P. is BREA X L.L.C. The managing member of BREA X L.L.C. is Blackstone Holdings II L.P. The general partner of Blackstone Holdings II L.P. is

Blackstone Holdings I/II GP L.L.C.

Blackstone Private Equity Strategies Associates L.P. is the general partner of each of BXPE Nucleus Lux Holdco L.P.

and BXPE Nucleus US Holdco L.P. The general partner of Blackstone Private Equity Strategies Associates L.P. is BXPEA L.L.C. The managing member of BXPEA L.L.C. is Blackstone Holdings II L.P. The general partner of Blackstone Holdings II L.P. is

Blackstone Holdings I/II GP L.L.C.

BTO Holdings Manager IV L.L.C. is the general partner of BTO Nucleus Holdings DE L.P. The sole member of BTO Holdings

Manager IV L.L.C. is BTO DE GP – NQ L.L.C. The sole member of BTO DE GP – NQ L.L.C. is Blackstone Holdings II L.P. The general partner of Blackstone Holdings II L.P. is Blackstone Holdings I/II GP L.L.C.

Blackstone Inc. is the sole member of Blackstone Holdings I/II GP L.L.C. and Blackstone Holdings III GP Management L.L.C. The sole holder of the Series II preferred stock of Blackstone Inc. is Blackstone Group Management L.L.C. Blackstone Group Management L.L.C. is wholly-owned by Blackstone’s senior managing

directors and controlled by its founder, Stephen A. Schwarzman. Each of the Blackstone entities described in this footnote and Mr. Schwarzman (other than to the extent it or he directly holds securities as described herein) may be deemed to beneficially own the securities directly or indirectly controlled by such Blackstone entities or him, but each disclaims beneficial ownership of such securities. The address of each of such

Blackstone entities and Mr. Schwarzman is c/o Blackstone Inc., 345 Park Avenue, New York, New York 10154.

As described under “Prospectus

Supplement Summary—Recent Developments,” on June 29, 2026, the company entered into an agreement to purchase from Blackstone all of Blackstone’s interests in the joint ventures. For more information about the company’s relationship with Blackstone and its affiliates, see “Certain Relationships and Related Party Transactions” in our definitive proxy statement on Schedule 14A, filed with the SEC on April 17, 2026, which is incorporated herein by reference.

UNDERWRITING

Morgan Stanley & Co. LLC is acting as the sole underwriter of the offering. Subject to the terms and conditions set forth in an underwriting agreement among us, the selling stockholders and the underwriter, the selling stockholders have agreed to sell to the underwriter, and the underwriter has agreed to purchase from the selling stockholders, shares of common stock.

Subject to the terms and conditions set forth in the underwriting agreement, the underwriter has agreed to purchase all of the shares sold under the underwriting agreement if any of these shares are purchased.