MGNI Form 4: Executive sell-to-cover and 10b5-1 sales disclosed

Rhea-AI Filing Summary

Magnite insider sales by President, Revenue Sean Patrick Buckley reported two non-derivative sales of Common Stock: 10,886 shares sold on 08/18/2025 at a weighted average price of $23.85 and 9,315 shares sold on 08/19/2025 at a weighted average price of $23.42, leaving the reporting person with 336,508 and then 327,193 shares beneficially owned after each transaction respectively. The filing states the first sale was to satisfy tax withholding on vested restricted stock units and was not discretionary. The second sale was executed under a Rule 10b5-1 trading plan adopted on November 24, 2023. The filer signed by attorney-in-fact.

Positive

• Transparent disclosure of share counts, weighted average prices, and remaining beneficial ownership
• Use of Rule 10b5-1 plan demonstrates preplanned sales and reduces concerns about opportunistic insider trading
• Sell-to-cover for tax withholding indicates the sale was non-discretionary and tied to RSU settlement

Negative

• Insider sold a total of 20,201 shares, modestly reducing beneficial ownership from 336,508 to 327,193 shares
• Weighted average sale prices indicate sales in a $23.18–$24.10 range, which may reflect realized liquidity at current market levels

Insights

Securities Analyst

TL;DR: Routine insider sell-to-cover and 10b5-1 transactions, indicating tax settlement and preplanned disposition rather than ad-hoc liquidation.

The transactions consist of a mandated sell-to-cover for tax withholding on vested RSUs and a sale under an existing Rule 10b5-1 plan. Both are common mechanisms for executives to satisfy tax obligations and to systematically monetize equity while reducing risk of insider trading claims. The sizes—10,886 and 9,315 shares—are modest relative to the remaining beneficial ownership (327k+ shares) and do not by themselves indicate a change in control or material shift in alignment with shareholders. Disclosure of the 10b5-1 plan adoption date improves transparency and reduces informational asymmetry for investors.

Corporate Governance Expert

TL;DR: Governance controls appear to be functioning: mandatory tax withholding and 10b5-1 plan usage limit insider trading risk.

The filing documents appropriate corporate and personal governance steps: the issuer used sell-to-cover to satisfy withholding on vested RSUs, and the reporting person used a 10b5-1 plan for subsequent sales. These mechanisms align with best practices for executive compensation settlement and preplanned dispositions, reducing concerns about opportunistic trading. The reporting remains specific about quantities, prices (weighted average for the 08/19 sale) and residual holdings, which supports transparency. No indication of unexpected departures or governance disputes is present in the disclosure.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Buckley Sean Patrick

(Last) (First) (Middle)

C/O MAGNITE, INC.

1250 BROADWAY, 15TH FLOOR

(Street)

NEW YORK NY 10001

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
MAGNITE, INC. [ MGNI ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	President, Revenue

3. Date of Earliest Transaction (Month/Day/Year)
08/18/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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	08/18/2025		S(1)		10,886	D	$23.85	336,508	D
Common Stock	08/19/2025		S(2)		9,315	D	$23.42(3)	327,193	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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

Explanation of Responses:

1. These shares were sold to cover the Reporting Person's tax obligation resulting from the settlement of vested Restricted Stock Units. The sale is mandated by the Issuer's election to require the satisfaction of tax withholding obligations to be funded by sell to cover transactions and does not represent a discretionary transaction by the Reporting Person.

2. The reported transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on November 24, 2023.

3. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $23.18 to $24.10, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote to this Form 4.

	/s/ Aaron Saltz, attorney-in-fact	08/20/2025
	** Signature of Reporting Person	Date
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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What transactions did the Magnite (MGNI) insider report?

The reporting person sold 10,886 shares on 08/18/2025 at a weighted average price of $23.85 and 9,315 shares on 08/19/2025 at a weighted average price of $23.42.

Why were the shares sold according to the Form 4 for MGNI?

The Form 4 states the first sale was to satisfy tax withholding on vested RSUs and the second sale was executed under a Rule 10b5-1 trading plan.

How many shares does the reporting person own after these MGNI transactions?

After the 08/18/2025 sale the reporting person beneficially owned 336,508 shares and after the 08/19/2025 sale they beneficially owned 327,193 shares.

Was the 10b5-1 trading plan adoption date disclosed in the MGNI filing?

Yes. The Form 4 discloses the 10b5-1 trading plan was adopted on November 24, 2023.

Do these transactions appear discretionary according to the filing?

No. The filing states the sell-to-cover was mandated by the issuer and the other sale was under a preexisting 10b5-1 plan, indicating the transactions were not ad-hoc discretionary trades.