Magnite (MGNI) President, Revenue reports routine tax-withholding share forfeiture

Rhea-AI Filing Summary

MAGNITE, INC. President, Revenue Sean Patrick Buckley reported a routine share disposition related to tax withholding. On the vesting of restricted stock units, 12,019 shares of common stock were forfeited at a value of $12.82 per share to satisfy tax obligations under a mandatory arrangement. After this non-discretionary forfeiture, Buckley directly holds 392,747 shares, which include 1,767 shares acquired on May 15, 2026 under the company’s Employee Stock Purchase Plan.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider Buckley Sean Patrick

Role President, Revenue

Type	Security	Shares	Price	Value
Tax Withholding	Common Stock	12,019	$12.82	$154K

Holdings After Transaction: Common Stock — 392,747 shares (Direct, null)

Footnotes (1)

1. Represents the non-discretionary forfeiture of shares on behalf of the Reporting Person pursuant to an arrangement mandated by the Issuer to cover the tax withholding obligations associated with the vesting of restricted stock units. Includes 1,767 shares acquired by the Reporting Person on May 15, 2026 under the Issuer's Employee Stock Purchase Plan.

Key Figures

Tax-withholding shares forfeited: 12,019 shares Deemed value per share: $12.82 per share Shares held after transaction: 392,747 shares +1 more

4 metrics

Tax-withholding shares forfeited 12,019 shares Forfeited to cover tax obligations on RSU vesting

Deemed value per share $12.82 per share Value used for tax-withholding disposition

Shares held after transaction 392,747 shares Direct common stock holdings following forfeiture

ESPP shares included 1,767 shares Acquired May 15, 2026 under Employee Stock Purchase Plan

Key Terms

restricted stock units, Employee Stock Purchase Plan, tax withholding obligations, non-discretionary forfeiture

4 terms

restricted stock units financial

"associated with the vesting of restricted stock units"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

Employee Stock Purchase Plan financial

"acquired by the Reporting Person on May 15, 2026 under the Issuer's Employee Stock Purchase Plan"

An employee stock purchase plan is a company program that lets workers buy shares through small payroll deductions, often at a discount to the market price and after a set offering period. Think of it like a workplace savings plan that turns into ownership: it encourages employees to share in the company’s success and can create predictable buying or selling of stock that investors watch because it affects supply, demand and employee incentives.

tax withholding obligations financial

"to cover the tax withholding obligations associated with the vesting of restricted stock units"

non-discretionary forfeiture financial

"Represents the non-discretionary forfeiture of shares on behalf of the Reporting Person"

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Form 4 Insider Transactions: What Each Field Means →

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).

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, 9TH FLOOR

(Street)

NEW YORK NEW YORK 10001

(City) (State) (Zip)

UNITED STATES

(Country)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/15/2026

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

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

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

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	05/15/2026		F(1)		12,019	D	$12.82	392,747(2)	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. Represents the non-discretionary forfeiture of shares on behalf of the Reporting Person pursuant to an arrangement mandated by the Issuer to cover the tax withholding obligations associated with the vesting of restricted stock units.

2. Includes 1,767 shares acquired by the Reporting Person on May 15, 2026 under the Issuer's Employee Stock Purchase Plan.

	/s/ Aaron Saltz, attorney-in-fact	05/19/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did MAGNITE (MGNI) report for Sean Patrick Buckley?

MAGNITE reported that Sean Patrick Buckley had 12,019 common shares forfeited to cover tax withholding on vested restricted stock units. This was a non-discretionary, issuer-mandated arrangement rather than an open-market sale or voluntary trade by the executive.

Was the MAGNITE (MGNI) insider transaction an open-market sale of shares?

No, the transaction was not an open-market sale. The 12,019 MAGNITE shares were forfeited automatically to satisfy tax withholding obligations triggered by vesting restricted stock units, as mandated by the company’s arrangement, rather than a discretionary sale decision.

How many MAGNITE (MGNI) shares does Sean Patrick Buckley hold after this Form 4 transaction?

Following the tax withholding forfeiture, Sean Patrick Buckley directly holds 392,747 MAGNITE common shares. This total includes 1,767 shares that he acquired on May 15, 2026 under the company’s Employee Stock Purchase Plan, according to the filing footnote.

What does the tax-withholding disposition on MAGNITE (MGNI) shares mean for investors?

The tax-withholding disposition reflects 12,019 MAGNITE shares forfeited to pay taxes on vested restricted stock units. Such non-discretionary events are common in equity compensation programs and typically do not signal a change in the executive’s outlook or a strategic decision to reduce holdings.

What role does Sean Patrick Buckley hold at MAGNITE (MGNI) in this Form 4 filing?

In this Form 4, Sean Patrick Buckley is identified as an officer of MAGNITE, serving as President, Revenue. The reported transaction concerns his equity compensation and related tax withholding, rather than a voluntary trading decision in the open market.