AppNexus

Leading independent ad tech platform prior to acquisition, now part of Microsoft Advertising

AppNexus was a pioneering cloud-based advertising technology platform founded in 2007 that provided programmatic advertising infrastructure for the digital advertising ecosystem. The company operated one of the largest independent ad exchanges and supply-side platforms (SSP), enabling publishers, advertisers, agencies, and networks to buy and sell digital advertising inventory in real-time through programmatic auctions. AppNexus distinguished itself by offering both buy-side and sell-side solutions, along with a robust marketplace that processed billions of ad impressions daily across display, video, mobile, and native advertising formats. At its peak, AppNexus was considered one of the most significant independent ad tech companies, competing directly with Google's DoubleClick and other major platforms. The company was acquired by AT&T in 2018 for approximately $1.6 billion and subsequently rebranded as Xandr. Following AT&T's divestiture strategy, Microsoft acquired Xandr in 2021, integrating it into Microsoft Advertising. AppNexus's technology and infrastructure continue to power significant portions of the programmatic advertising ecosystem under the Microsoft Advertising umbrella, serving major publishers, advertisers, and agencies globally.