Google Talk is a freeware voice over Internet protocol (VoIP) client application offered by Google Inc. The first beta version of the program was released on August 24, 2005. It is available for the Android operating system, Microsoft Windows (XP, Server 2003, Vista, and Windows 7), Intel Mac OS X 10.5 or later, GNU/Linux, and Google Chrome OS.
Instant messaging between the Google Talk servers and its clients uses an open protocol, XMPP, allowing users of other XMPP/Jabber clients to communicate with Google Talk users. VoIP in Google Talk uses an older version of what would later become the Jingle protocol. The technology used within the Google server network, however, is not publicly known.
Google Talk mobile clients are also available for the Palm Pre, BlackBerry, Android-based devices and is preloaded on the Nokia N900 smartphone.