AppNexus Inc.
Company typeSubsidiary
IndustryOnline advertising
Founded2007; 17 years ago (2007)
HeadquartersNew York City, United States
Area served
Key people
Michael Rubenstein (president)
ProductsInfrastructure as a service
Ad serving
Number of employees

Xandr, formerly known as AppNexus, is an American multinational technology company operating a cloud-based software platform that enables and optimizes programmatic online advertising.[1] Headquartered in the Flatiron District of New York City, the company has 23 offices in North America, Latin America, Europe, Asia and Australia.[citation needed]

AppNexus offers online auction infrastructure and technology for data management, optimization, financial clearing and support for directly negotiated advertising campaigns. It has both demand-side platform (DSP), supply-side platform (SSP), and ad serving functionalities. It integrates with advertising sources including Google's "Authorized Buyers" ad exchange, Magnite, Pubmatic and other aggregators.[2][3] It operates out of multiple data centers, including one in Amsterdam serving Europe and the Middle East, in a facility shared with Equinix.[4]

In 2016, AppNexus was ranked #21 on Forbes Magazine's "The Cloud 100" list.[5]

In June 2018, AT&T announced it was acquiring the company and putting it under its Xandr division as a subsidiary.[6] AppNexus was reportedly sold for $1.6 billion, while most news outlets speculated the company did not sell for less than $2 billion.[7]

In October 2019, Xandr purchased Clypd, a privately-held technology company focused on enabling programmatic buying of linear television advertising.[8]

In December 2021, AT&T announced that they had agreed to sell Xandr to Microsoft for an undisclosed price, subject to customary closing conditions, including regulatory reviews.[9]

Founders and financing

AppNexus was founded by former Right Media staff, CTO Brian O'Kelley, and Mike Nolet, product manager and director of analytics,[10] with Michael Rubenstein, a former vice president and general manager at Google DoubleClick, who joined AppNexus as president in September 2009.[11] The company was financially backed by Microsoft, Khosla Ventures, First Round Capital, Venrock,[12] Kodiak Venture Partners, Marc Andreessen, Ben Horowitz, and Ron Conway; as of 2015 the company had raised $250 million in financing. O'Kelley stepped down as CEO in October 2018.[13]


  1. ^ Stephanie Clifford (2010-03-12). "Instant Ads Set the Pace on the Web". The New York Times. Archived from the original on 17 March 2010. Retrieved 2010-03-12.
  2. ^ AppNexus (2010-03-12). "AppNexus Officially Launches Ad Platform Fueling the Real-Time Bidding Revolution in Display Advertising". Press release (Press release). PR Newswire. Archived from the original on 22 March 2010. Retrieved 2010-03-12.
  3. ^ "AppNexus Expands Video Buying, Adds New Video Demand Partners". Retrieved 2016-05-22.
  4. ^ Liz Gannes (2010-10-05). "AppNexus Raises $50M for Real-time Ad Platform: Tech News and Analysis «". Retrieved 2011-05-11.
  5. ^ "The Cloud 100". Forbes. Retrieved 17 November 2016.
  6. ^ "AT&T to Acquire AppNexus". 25 June 2018. Retrieved 23 December 2019.
  7. ^ "AT&T Will Acquire AppNexus | AdExchanger". AdExchanger. 2018-06-25. Retrieved 2018-07-13.
  8. ^ "Xandr Acquired Clypt in Move to Build Connevted TV Empire". 18 October 2019..
  9. ^ Foley, Mary Jo (December 21, 2021). "Microsoft to buy Xandr ad marketplace from AT&T". ZDNet. Retrieved December 21, 2021.
  10. ^ "Who We Are". AppNexus. Archived from the original on 17 May 2011. Retrieved 2011-05-11.
  11. ^ [1] Archived December 12, 2010, at the Wayback Machine
  12. ^ "AppNexus Secures $8 Million in Series B Funding". Archived from the original on 2012-06-14. Retrieved 2011-05-11.
  13. ^ Brian O’Kelley Steps Down As AppNexus CEO Published by on October 5, 2018, retrieved on September 11, 2019