Flock is a web browser that specialised in providing social networking and Web 2.0 facilities built into its user interface. Earlier versions of Flock used the Gecko rendering engine by Mozilla. Flock version 2.6.2 was the last version based on Mozilla Firefox. Starting with version 3, Flock was based on Chromium and used the WebKit rendering engine. Support for Flock browsers was discontinued in April 2011.