Who owns Xandr?
Microsoft owns Xandr. It bought the business from AT&T in a deal announced in December 2021 and closed in 2022. Xandr itself grew out of AT&T's 2018 purchase of AppNexus. Microsoft shut the buy-side platform, renamed Microsoft Invest, on 28 February 2026, but kept the sell-side Monetize SSP and its Curate tools.
AppNexus was one of the original independent exchanges and the birthplace of Prebid. AT&T bought it to build an addressable TV and data business, rebranding it Xandr. Microsoft acquired Xandr to power ads on its properties, including Microsoft Advertising and, for a time, Netflix's ad tier launch in 2022.
In May 2025 Microsoft announced it would retire the Invest DSP and later named Amazon DSP as its preferred partner for advertisers. Microsoft Monetize continues as an SSP and publisher ad server, and Microsoft Curate is its curation product.