A programming interface (API) for social networking sites from Google. Introduced in 2007, it was created to allow social networking applications to run on more than one site. Google's Orkut along with MySpace, Friendster and hi5 were the first sites to support the OpenSocial interface. An Open Platform OpenSocial was designed to provide an alternative to the Facebook Platform, which let people write applications for Facebook, but which would only run on Facebook. See Facebook.