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.

Kevin Marks is author of the weblog Epeus Epigone. He was Vice President of Web Services at BT. He became Principal Engineer for Technorati after working for both Apple and the BBC. At the TechCrunch event Realtime Stream Crunchup he announced that he would be joining BT to work together with JP Rangaswami. In May 2011 he began working at Salesforce.com. He is one of the founders of Microformats.

At the first BloggerCon, Marks discussed the power curve as it applies to weblogs:

The net changes the power law of the media curve. If you look at relative popularity on the web, using something like Technorati, you get a power curve that goes all the way down gradually, to the bottom where you see pages that got just a single click. If you look at popularity in the "real" world — best-selling books, or top music — the power curve drops like a stone from a very high level. That's because in order to get a book published, or a piece of music recorded, you have to convince somebody that you're going to sell a million copies. You end up in a zero-sum game, where people pour enormous resources into being the number one, because number two is only half as good. The promise of the net is that the power of all those little links can outweigh the power of the top ten.