X0609 4 2026-09-08 0 0001595974 MAGNITE, INC. MGNI 0001700262 Evans Katie Seitz false C/O MAGNITE, INC. 1250 BROADWAY, 9TH FLOOR NEW YORK NY 10001 0 1 0 0 See Remarks 1 Common Stock 2026-09-08 4 M 0 13546 5.16 A 499182 D Common Stock 2026-09-08 4 S 0 32285 23.63 D 466897 D Common Stock 2026-09-09 4 S 0 11100 23.46 D 455797 D Employee Stock Option (Right to Buy) 5.16 2026-09-08 4 M 0 13546 0 D 2029-02-27 Common Stock 13546 0 D The reported transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 8, 2026. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $23.465 to $23.91, 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 to this Form 4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $23.095 to $24.00, 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 to this Form 4. The stock options have fully vested and are immediately exercisable. Granted as compensation for services. The amount reported in Column 9 reflects a correction to the number of derivative securities beneficially owned directly by the Reporting Person. A prior report inadvertently understated the number of derivative securities beneficially owned directly by the Reporting Person by 13,546 shares due to an administrative error. This correction does not reflect any purchase, sale or other transaction by the Reporting Person. President, Product & Operations /s/ Aaron Saltz, attorney-in-fact 2026-09-10