AppNexus

Former leading independent programmatic advertising technology platform

AppNexus was one of the most influential independent ad tech companies, providing a comprehensive programmatic advertising platform that enabled buyers and sellers to trade digital advertising inventory in real-time. Founded in 2007, the company built one of the largest and most sophisticated ad exchanges and supply-side platforms (SSP) in the industry, processing trillions of ad impressions annually and serving major publishers, advertisers, and ad tech companies globally. The platform offered both buy-side and sell-side solutions, including a demand-side platform (DSP), supply-side platform (SSP), and ad exchange infrastructure. AppNexus was known for its technological innovation, particularly in real-time bidding (RTB) technology and its ability to handle massive scale. The company competed directly with Google's DoubleClick and other major ad tech platforms. In 2018, AT&T acquired AppNexus for approximately $1.6 billion as part of its strategy to build a digital advertising business following its acquisition of Time Warner. AppNexus was subsequently integrated into AT&T's advertising and analytics division, which was later rebranded as Xandr. In 2021, AT&T sold Xandr (including the former AppNexus technology) to Microsoft, effectively ending the AppNexus brand's independent existence.