Xandr, formerly known as AppNexus, is an American multinational technology company operating a cloud-based software platform that enables and optimizes programmatic online advertising. Headquartered in the Flatiron District of New York City, the company has 23 offices in North America, Latin America, Europe, Asia and Australia. In 2016, AppNexus was ranked #21 on Forbes Magazine's "The Cloud 100" list. In October 2019, Xandr purchased Clypd, a privately-held technology company focused on enabling programmatic buying of linear television advertising.