Google AdSense is a program run by Google that allows publishers in the Google Network of content sites to serve automatic text, image, video, or interactive media advertisements, that are targeted to site content and audience. These advertisements are administered, sorted, and maintained by Google, and they can generate revenue on either a per-click or per-impression basis. Google service, but discontinued it in October 2008 in favor of a DoubleClick offering (also owned by Google). In Q1 2011, Google earned US $2.43 billion ($9.71 billion annualized), or 28% of total revenue, through Google AdSense.
Google launched its AdSense program, originally named content targeting advertising in March 2003. The AdSense name was originally used by Applied Semantics, a competitive offering to AdSense and then adopted by Google after Google acquired Applied Semantics in April 2003. Applied Semantics was started in 1998 by Gilad Elbaz and Adam Weissman. Some advertisers complained that AdSense yielded worse results than AdWords, since it served ads that related contextually to the content on a web page and that content was less likely to be related to a user's commercial desires than search results. For example, someone browsing a blog dedicated to flowers was less likely to be interested in ordering flowers than someone searching for terms related to flowers. As a result, in 2004 Google allowed its advertisers to opt out of the AdSense network.
Paul Buchheit, the founder of Gmail, had the idea to run ads within Google's e-mail service. But he and others say it was Susan Wojcicki, with the backing of Sergey Brin, who organized the team that adapted that idea into an enormously successful product. By early 2005 AdSense accounted for an estimated 15 percent of Google's total revenues.
In 2009, Google AdSense announced that it would now be offering new features, including the ability to "enable multiple networks to display ads".
In February 2010, Google AdSense started using search history in contextual matching to offer more relevant ads.
On January 21, 2014, Google AdSense launched Direct Campaigns, a tool where publishers may directly sell ads.