RUBI The Rubicon Project Inc

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 OF SECURITIES                                                                                   
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940                       

1. Name and Address of Reporting Person * Prusz Joseph R	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) Global Chief Revenue Officer
(Last)          (First)          (Middle) C/O MAGNITE, INC., 12181 BLUFF CREEK DRIVE, 4TH FLOOR	3. Date of Earliest Transaction (MM/DD/YYYY) 4/1/2021
(Street) PLAYA VISTA, CA 90094 (City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	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. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. 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	4/1/2021		A		23820 (1)	A	$0.00 (2)	422558	D

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. 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		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 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 Option (right to buy)	$42.80	4/1/2021		A		17726		(3)	4/1/2031	Common Stock	17726	$0.00 (2)	17726	D

Explanation of Responses:
(1)	Represents restricted stock units that vest as follows: 6,451 on May 15, 2022, 1,489 on each August 15, November 15, February 15, and May 15 thereafter until February 15, 2025 and 990 on May 15, 2025, subject to continued service to the Issuer through each vesting date. This equity grant may be subject to accelerated vesting in the event the Reporting Person's employment is terminated under certain circumstances.
(2)	Equity grant under the Company's 2014 Equity Incentive Plan.
(3)	25% of the total number of shares underlying this option will vest on April 1, 2022 and the remaining shares vest 1/36 per month over the next 36 months thereafter, subject to continued service to the Issuer through each vesting date. This equity grant may be subject to accelerated vesting in the event the Reporting Person's employment is terminated under certain circumstances.

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Prusz Joseph R C/O MAGNITE, INC. 12181 BLUFF CREEK DRIVE, 4TH FLOOR PLAYA VISTA, CA 90094			Global Chief Revenue Officer

Signatures
/s/ Aaron Saltz, attorney-in-fact		4/5/2021
**Signature of Reporting Person		Date