X0306 4 2021-08-26 0 0001595974 MAGNITE, INC. MGNI 0001100612 BARRETT MICHAEL G. C/O MAGNITE, INC. 6080 CENTER DRIVE, 4TH FLOOR LOS ANGELES CA 90045 1 1 0 0 CEO Common Stock 2021-08-26 4 A 0 136939 0.00 A 1479368 D Performance Stock Units 2021-08-26 4 A 0 379635 0.00 A Common Stock 379635 379635 D Represents restricted stock units that vest as to 1/3 on each of August 15, 2023, August 15, 2024 and August 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. Each performance stock unit ("PSU") represents a contingent right to receive on vesting one share of the Issuer's common stock. The PSUs are subject to both performance-based and time-based vesting requirements. The performance-based requirement for 1/3 of the units will be satisfied if the Issuer achieves share price targets of $60, $80 and $100 over 60 consecutive trading days during a performance period commencing on Aug. 26, 2022 and ending on Aug. 26, 2026, or on such earlier date as the Reporting Person is no longer serving as the Issuer's CEO or Executive Chairman of the Board of Directors. To the extent any of the performance-based requirements are met, the Reporting Person must also provide continued service to the Issuer through at least Aug. 26, 2024 to receive any shares of common stock underlying the PSUs and through Aug. 26, 2026 to receive all of the shares of common stock underlying the PSUs that have satisfied the applicable performance-based requirements. The grant may be subject to accelerated vesting in the event the Reporting Person's employment is terminated under certain circumstances. Equity grant under the Issuer's 2014 Equity Incentive Plan. /s/ Aaron Saltz, attorney-in-fact 2021-08-30