X0306 4 2022-05-15 0 0001595974 MAGNITE, INC. MGNI 0001100612 BARRETT MICHAEL G. C/O MAGNITE, INC. 1250 BROADWAY,15TH FLOOR NEW YORK NY 10001 1 1 0 0 CEO Common Stock 2022-05-15 4 F 0 32422 10.59 D 1541468 D 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 1,129 shares acquired by the Reporting Person on May 15, 2022 under the Issuer's employee stock purchase plan. /s/ Aaron Saltz, attorney-in-fact 2022-05-17