Sec Form 4 Filing - ZWARENSTEIN BARRY @ ON24 INC. - 2026-04-01

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person ZWARENSTEIN BARRY 2. Issuer Name and Ticker or Trading Symbol ON24 INC. [ ONTF] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O ON24, INC., 301 HOWARD STREET, SUITE 1100 3. Date of Earliest Transaction (MM/DD/YY) 04/01/2026 (Street) SAN FRANCISCO, CA94105 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 04/01/2026 D 154,586 D 0 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Options (Right to buy) $ 6.88 04/01/2026 D 110,834 ( 2 ) 08/28/2030 Common Stock 110,834 $ 0 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other ZWARENSTEIN BARRY C/O ON24, INC. 301 HOWARD STREET, SUITE 1100 SAN FRANCISCO, CA94105 X Signatures /s/ ZWARENSTEIN BARRY by Charles Rogerson, as Attorney-in-Fact 04/02/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Pursuant to the Agreement and Plan of Merger, dated as of December 29, 2025 (the "Merger Agreement") among the Issuer, Cvent Atlanta, LLC ("Parent"), and Summit Sub Corp. ("Merger Sub"), on April 1, 2026, Merger Sub merged with and into the Issuer, with the Issuer continuing as the surviving company and a wholly-owned subsidiary of Parent (the "Merger"). At the effective time of the Merger, each outstanding share of Issuer common stock was automatically canceled and converted into the right to receive cash in an amount equal to $8.10 per share, without interest, with similar treatment for outstanding RSUs. ( 2 )At the effective time of the Merger, each outstanding option to purchase Issuer common stock was automatically canceled and converted into the right to receive cash in an amount equal to $8.10 less the exercise price per share of such option.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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