X0306 4 2021-04-01 0 0001595974 MAGNITE, INC. MGNI 0001721039 Prusz Joseph R C/O MAGNITE, INC. 12181 BLUFF CREEK DRIVE, 4TH FLOOR PLAYA VISTA CA 90094 0 1 0 0 Global Chief Revenue Officer Common Stock 2021-04-01 4 A 0 23820 0.00 A 422558 D Stock Option (right to buy) 42.80 2021-04-01 4 A 0 17726 0.00 A 2031-04-01 Common Stock 17726 17726 D 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. Equity grant under the Company's 2014 Equity Incentive Plan. 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. /s/ Aaron Saltz, attorney-in-fact 2021-04-05