Each Representing a 1/20th Interest in a Share of% Series B Mandatory Convertible Preferred Stock Alphabet Inc. % Series B Mandatory Convertible Preferred Stock We are offering 150,000,000 of our Series B Depositary Shares (“Series B Depositary Shares”), each of which represents a1/20th interest in a share of our% Series B Mandatory Convertible Preferred Stock, par value $0.001 per share(“Series B Mandatory Convertible Preferred Stock”). The shares of Series B Mandatory Convertible Preferred Stock will bedeposited with Computershare Trust Company, N.A. and Computershare Inc., acting as joint bank depositary (the “bankdepositary”), pursuant to a deposit agreement. Holders of the Series B Depositary Shares will be entitled to a proportionalfractional interest in the rights and preferences of the Series B Mandatory Convertible Preferred Stock, including conversion,dividend, liquidation and voting rights, subject to the provisions of such deposit agreement. Dividends on our Series B Mandatory Convertible Preferred Stock will be payable on a cumulative basis when, as and ifdeclared by our board of directors, or an authorized committee of our board of directors, at an annual rate of% on theliquidation preference of $1,000 per share. We may pay declared dividends in cash or, subject to certain limitations, in shares ofour ClassC capital stock, par value $0.001 per share (“ClassC Capital Stock”), or in any combination of cash and shares of ourClassC Capital Stock on February15, May15, August15 and November15 of each year, commencing on, and including,August15, 2026 and ending on, and including, May15, 2029. Each share of our Series B Mandatory Convertible Preferred Stock has a liquidation preference of $1,000 (and, correspondingly,each Series B Depositary Share represents a liquidation preference of $50). Unless earlier converted, each share of our Series BMandatory Convertible Preferred Stock will automatically convert on the second business day immediately following the lasttrading day of the final averaging period (as defined below) into betweenandshares of our ClassC CapitalStock, subject to anti-dilution adjustments. The number of shares of our ClassC Capital Stock issuable on conversion will bedetermined based on the average VWAP (as defined herein) of our ClassC Capital Stock over the 20-trading-day periodbeginning on, and including, the 21st scheduled trading day prior to May15, 2029, which we refer to herein as the “finalaveraging period.” At any time prior to May15, 2029, a holder of 20 Series B Depositary Shares may cause the bank depositaryto convert one share of our Series B Mandatory Convertible Preferred Stock, on such holder’s behalf, into a number of shares ofour ClassC Capital Stock equal to the minimum conversion rate of, subject to anti-dilution adjustments. If a holder of20 Series B Depositary Shares causes the bank depositary to convert one share of our Series B Mandatory Convertible PreferredStock, on such holder’s behalf, during a specified period beginning on the effective date of a fundamental change (as describedherein), the conversion rate will be adjusted under certain circumstances, and such holder will also be entitled to a make-wholedividend amount (as described herein). Prior to this offering, there has been no public market for the Series B Depositary Shares or the Series B MandatoryConvertible Preferred Stock. We intend to apply to list the Series B Depositary Shares on The Nasdaq Global SelectMarket under the symbol “GOOGN.” Our ClassC Capital Stock is listed on The Nasdaq Global Select Market underthe symbol “GOOG.” The information contained in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. Thispreliminary prospectus supplement and the accompanying prospectus are not an offer to sell the securities and are not soliciting an offer to buy the(continued on inside front cover) Table of Contents See “Risk Factors” beginning on page S-16 of this prospectus supplement and in our Annual Report on Form 10-K for the fiscal year endedDecember31, 2025 and our Quarterly Report on Form 10-Q for the fiscal quarter ended March31, 2026 for a discussion of certain risks thatshould be considered in connection with an investment in our Series B Depositary Shares. (1)Assumes no exercise of the underwriters’ over-allotment option to purchase additional Series B Depositary Shares described below.(2)See the section titled “Underwriting” beginning on page S-74 of this prospectus supplement for a description of the compensation payable to theunderwriters. We have granted the underwriters the option to purchase up to an additional 22,500,000 Series B Depositary Shares from us at the public offering priceless the underwriting discounts within a 13-day period beginning on, and including, the date we first issue the Series B Depositary Shares, solely tocover over-allotments, if any. Neither the Securities and Exchange Commission (the “SE