144 0001865116 XXXXXXXX LIVE 0001595974 MAGNITE, INC. 001-36384 1250 BROADWAY 15TH FLOOR NEW YORK NY 10001 212-243-2769 Sean Patrick Buckley Officer Common Morgan Stanley Smith Barney LLC Executive Financial Services

1 New York Plaza 8th Floor New York NY 10004

14461 342725.70 142399305 08/18/2025 NASDAQ Common 08/15/2025 Restricted Stock Unit- See Remarks Issuer N 14461 08/15/2025 Equity Compensation N Sean Buckley

c/o Magnite, Inc. 1250 Broadway, 15th Floor New York NY 10001

Common 05/16/2025 9692 152491.04 Shares sold to cover the Reporting Person's tax obligation resulting from settlement of vested Restricted Stock Units. The sale is mandated by the Issuer's election to require the satisfaction of tax withholding obligations to be funded by sell to cover transactions and does not represent a discretionary transaction by the Reporting Person. 08/15/2025 Aaron Saltz, attorney-in-fact for Sean Buckley