X0306 4 2021-07-09 0 0001595974 MAGNITE, INC. MGNI 0001807986 Saltz Aaron C/O MAGNITE, INC. 6080 CENTER DRIVE, 4TH FLOOR LOS ANGELES CA 90045 0 1 0 0 General Counsel Common Stock 2021-07-09 4 M 0 1791 3.61 A 268106 D Common Stock 2021-07-09 4 S 0 4195 32.66 D 263911 D Common Stock 2021-07-09 4 S 0 805 33.58 D 263106 D Stock Option (Right to Buy) 3.61 2021-07-09 4 M 0 1791 0.00 D 2028-02-27 Common Stock 1791 45391 D This exercise and subsequent sales were made pursuant to a Rule 10b5-1 Trading Plan adopted by the Reporting Person. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $32.365 to $33.21, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $33.48 to $33.68, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. 25% of the total number of shares underlying this option vested on February 14, 2019 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. Equity grant under the Company's 2014 Equity Incentive Plan. /s/ Aaron Saltz 2021-07-13