The Open Collaboration Services (OCS) is an open and vendor independent modern REST based API for integration of web communities and web based services into desktop and mobile applications. It allows to exchange relevant data from a Social Network between the site and clients such as other websites and applications or widgets running locally on the user's machine or mobile device. The protocol has been designed so that all applications can access multiple services providing OCS APIs.

The API was designed by openDesktop.org as part of the Social Desktop especially as a cross desktop backend provider.[1] The API got standardised by freedesktop.org so that third party provider are able to implement OCS API.

• Social Desktop, the home of the OCS API.
• http://freedesktop.org/wiki/Specifications/open-collaboration-services
• Open_Collaboration_Services