Exhibit 99.1 Magnite Reports Fourth Quarter and Full-Year 2023 Results Total Revenue up 7% & Contribution ex-TAC(1) up 6% in Fourth Quarter Adjusted EBITDA Margin(2) of 43% in Fourth Quarter Full-Year 2023 CTV Ad Spend(3) Growth Over 20% NEW YORK – February 28, 2024 – Magnite (NASDAQ: MGNI), the world's largest independent sell-side advertising company, today reported its results of operations for the fourth quarter and year ended December 31, 2023. Recent Highlights: • Revenue of $186.9 million for Q4 2023 ...