X0306 4 2021-04-01 0 0001595974 MAGNITE, INC. MGNI 0001100612 BARRETT MICHAEL G. C/O MAGNITE, INC. 12181 BLUFF CREEK DRIVE, 4TH FLOOR PLAYA VISTA CA 90094 1 1 0 0 CEO Common Stock 2021-04-01 4 A 0 41742 0.00 A 1601678 D Employee Stock Option (right to buy) 42.80 2021-04-01 4 A 0 54358 0.00 A 2031-04-01 Common Stock 54358 54358 D Performance Stock Units 2021-04-01 4 A 0 26291 0.00 A Common Stock 26291 26291 D Represents restricted stock units that vest as follows: 11,305 on May 15, 2022, 2,609 on each August 15, November 15, February 15, and May 15 thereafter until February 15, 2025 and 1,738 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. Each performance stock unit ("PSU") represents a contingent right to receive on vesting one share of the issuer's common stock. Vesting of the PSU will be determined based on the issuer's total stockholder return ("TSR") for the three-year period beginning on the grant date of the award relative to the TSRs of the companies in the Russell 2000 index over that period. The number of PSUs reported in column 5 reflects the target number of PSUs subject to the award. The award is eligible to vest as to 0% to 150% of the target number of PSUs. /s/ Aaron Saltz, attorney-in-fact 2021-04-05