Elgg is an open-source social networking service. Elgg allows users to build customized social networks for their groups, workplace, campus, and friends.
The Elgg API allows developers to access and integrate the functionality of Elgg with other applications and to create new applications. Some example API methods include building APIs, managing users, and retrieving network information.
A project of the Elgg Foundation, Elgg is a free open source social networking engine licensed to users under the GNU Public License v2. The REST Elgg API allows developers to integrate Elgg and offer new apps for it. To give a sense of its size, 1,646 plugins have been created so far by the user community, with nearly 3 million downloads. Examples of plugins include blogs, forums, social bookmarks.