Meta Platforms files 424B5: prospectus (424B)

The information in this prospectus supplement and accompanying prospectus is not complete and may be changed. This prospectus supplement and the accompanying prospectus are not an offer to sell these securities, and we are not soliciting offers to buy these securities, in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED OCTOBER 26, 2026

PRELIMINARY PROSPECTUS SUPPLEMENT (To Prospectus dated October 26, 2026)

Each Representing a 1/20th Interest in a Share of

% Series A Mandatory Convertible Preferred Stock

Meta Platforms, Inc.

We are offering 250,000,000 of our Series A Depositary Shares (“Series A Depositary Shares”), each of which represents a 1/20th interest in a share of our % Series A Mandatory Convertible Preferred Stock, par value $0.000006 per share (“Series A Mandatory Convertible Preferred Stock”). The shares of Series A Mandatory

Convertible Preferred Stock will be deposited with Computershare Trust Company, N.A. and Computershare Inc., acting as joint bank depositary (the “bank depositary”), pursuant to a deposit agreement. Holders of the Series A

Depositary Shares will be entitled to a proportional fractional interest in the rights and preferences of the Series A Mandatory Convertible Preferred Stock, including conversion, dividend, liquidation and voting rights, subject to the provisions of such deposit agreement.

Dividends on our Series A Mandatory Convertible Preferred Stock will initially be payable on a cumulative basis when, as and if declared by our board of directors, or an authorized committee of our board of directors, at an annual rate of % on the liquidation preference of $1,000 per share. We may pay declared dividends in cash or, subject to certain limitations, in shares of our Class A common stock, par value $0.000006 per share (“Class A Common Stock”), or in any combination of cash and shares of our Class A Common Stock on February 15, May 15, August 15 and November 15 of each year, commencing on, and including, February 15, 2027 and ending on, and including, August 15, 2029. Following the Class C Dividend Trigger Date (as herein defined), any declared dividends may be payable in cash or, subject to certain limitations, in shares of our Class C Common Stock (as defined below) or in any combination of cash and shares of our Class C Common Stock.

Each share of our Series A Mandatory Convertible Preferred Stock has a liquidation preference of $1,000 (and, correspondingly, each

Series A Depositary Share represents a liquidation preference of $50). Unless earlier converted, each share of our Series A Mandatory Convertible Preferred Stock will automatically convert on the second business day immediately following the last trading day of the final averaging period (as defined below) into between and shares of our Class A Common Stock, subject to anti-dilution adjustments; provided that, if the Class C Trigger Event (as herein defined) occurs, unless earlier converted, each share of our Series A Mandatory Convertible Preferred Stock will automatically convert on the second business day immediately following the last trading day of the final averaging period into a number of shares of our Class C Common Stock not less than the then-current minimum conversion rate nor greater than the then-current maximum conversion rate (each as herein defined). The number of shares of our Class A

Common Stock or our Class C Common Stock, as the case may be, issuable upon such conversion will be determined based on the average VWAP (as defined herein) of our Class A Common Stock or our Class C Common Stock, as the case may be, over the 20-trading-day period beginning on, and including, the 21st scheduled trading day prior to August 15, 2029, which we refer to herein as the “final averaging period.” At any time on or after the 50th trading day immediately following the Class C Dividend Trigger Date (as herein defined) and prior to August 15, 2029, a holder of 20 Series A Depositary Shares may cause the bank depositary to convert one share of our Series A Mandatory Convertible Preferred Stock, on such holder’s behalf, into a number of shares of our Class C Common Stock equal to the then-current minimum conversion rate. If a holder of 20 Series A Depositary Shares causes the bank depositary to convert one share of our Series A Mandatory Convertible Preferred Stock, on such holder’s behalf, during a specified period beginning on the fundamental change reference date with respect to a fundamental change (as described herein), the conversion rate will be adjusted under certain circumstances, and such holder will also be entitled to a make-whole dividend amount (as described herein).

The following summary contains basic information about the Series A Depositary Shares and this offering. It does not contain all of the information that may be important to you. For a more complete understanding of this offering, we encourage you to read this entire prospectus supplement and the accompanying prospectus.

Issuer Meta Platforms, Inc., a Delaware corporation

Series A Depositary Shares offered 250,000,000 Series A Depositary Shares, each of which represents a 1/20th interest in a share of our Series A Mandatory Convertible Preferred Stock. Each Series A Depositary Share entitles the holder of such Series A Depositary Share, through the bank depositary, to a proportional fractional interest in the rights and preferences of such share of Series A Mandatory Convertible Preferred Stock, including conversion, dividend, liquidation and voting rights, subject to the terms of the deposit agreement.

Underwriters’ option to purchase additional Series A Depositary Shares We have granted the underwriters a 30-day option to purchase up to 37,500,000 additional Series A Depositary Shares, at the public offering price, less the underwriting discounts, solely to cover over-allotments, if any.

Public offering price $50 per Series A Depositary Share

Liquidation preference $1,000 per share of our Series A Mandatory Convertible Preferred Stock (equivalent to $50 per Series A Depositary Share).

Class C Trigger Event A “Class C Trigger Event” will be deemed to have occurred if, on or prior to April 15, 2029, we issue, in connection with the Class C Dividend, shares of Class C Common Stock that are approved for listing, subject to official notice of issuance, on the Nasdaq Global Select Market, the Nasdaq Global Market or the New York Stock Exchange.

Class C Dividend The “Class C Dividend” means (x) the Declared Class C Dividend or (y) any reclassification or recapitalization (in each case, other than through a merger) of each share of Class A Common Stock outstanding into one share of Class A Common Stock and one share of Class C Common Stock, where such reclassification or recapitalization is economically equivalent to the Declared Class C Dividend.