X0609 4 2026-07-15 0001595974 MAGNITE, INC. MGNI 0001100612 BARRETT MICHAEL G. false C/O MAGNITE, INC. 1250 BROADWAY, 9TH FLOOR NEW YORK NY 10001 true true false false CEO true Common Stock 2026-07-15 4 M false 38596 5.80 A 441670 D Common Stock 2026-07-15 4 S false 38596 20.35 D 403074 D Employee Stock Option (Right to Buy) 5.80 2026-07-15 4 M false 38596 0 D 2027-03-17 Common Stock 38596 293968 D This exercise and subsequent sale were made pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 13, 2026. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $20.165 to $20.56, 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. /s/ Aaron Saltz, attorney-in-fact 2026-07-17