OpenSocial is a public specification that defines a component hosting environment (container) and a set of common application programming interfaces (APIs) for web-based applications. Initially it was designed for social network applications and was developed by Google along with MySpace and a number of other social networks. In more recent times it has become adopted as a general use runtime environment for allowing untrusted and partially trusted components from third parties to run in an existing web application. The OpenSocial Foundation has also moved to integrate or support numerous other open web technologies. This includes Oauth and OAuth 2.0, Activity Streams, and portable contacts, among others.

It was released November 1, 2007. Applications implementing the OpenSocial APIs will be interoperable with any social network system that supports them, including features on sites such as Hi5.com, 99factors.com, MySpace,orkut, Netlog,Sonico.com,Friendster,Ning, and Yahoo!.

Based on HTML and JavaScript, as well as the Google Gadgets framework, OpenSocial includes multiple APIs for social software applications to access data and core functions on participating social networks. Each API addresses a different aspect:. It also includes APIs for contacting arbitrary third party services on the web using a proxy system and OAuth for security.