Google Talk (GTalk) is a Windows and web-based application for voice over internet protocol (VOIP) and instant messaging, offered by Google. The first beta version of the program was released on August 24, 2005.

Instant messaging between the Google Talk servers and its clients uses an open protocol, XMPP, allowing users of other XMPP clients to communicate with Google Talk users. VoIP in Google Talk is based around the Jingle protocol. The technology used within the Google server network however is not publicly known.

The Google Talk client is currently only available for Windows (2000, XP, Server 2003, and Vista) and handhelds (the Blackberry, iPhone, and WinCE devices). With the release of the Google Talk gadget, users of all platforms supported by Adobe Flash Player can also use Google Talk. Many other XMPP clients are compatible with Google Talk, and support a variety of other platforms.

Interoperability

Google has announced that a major goal of the Google Talk service is interoperability. Google Talk uses XMPP to provide real-time extensible messaging and presence events, including offline messaging and voice mailing. On January 17, 2006, Google enabled server-to-server communications, federating itself with any Jabber server that supports the dialback protocol.

Product integration

On February 7, 2006, Gmail received chat functionality, using AjaxFact: date=June 2008 for server–browser communication, and was integrated with Google Talk. Users can send instant messages to other Gmail users. As it works within a browser, Google Talk does not need to be downloaded to send instant messages to Gmail users.

Conversation logs are automatically saved to a Chats area in the user's Gmail account. This allows users to search their chat logs and have them centrally stored in their Gmail accounts. It does not, however, appear possible to download chat logs that are not attached to an e-mail conversation.

Since November 8, 2006, Google has also integrated Google Talk with Orkut. This enables Google Talk users to interact with registered Orkut users, by sending and receiving 'scraps' within Orkut.

It is also possible to display the song currently playing on the computer. This music data is collected, if the user agrees to this, and displayed on the Google Music Trends page.

Encryption

The connection between the Google Talk client and the Google Talk server is encrypted, except when using Gmail's chat over HTTP, a federated network that doesn't support encryption, or when using a proxy like IMLogic. End-to-end messages are unencrypted. Google plans to add support for chat and call encryption in a future release. Some XMPP clients natively support encryption with Google Talk's servers. It is possible to have end-to-end encryption over the GTalk network using OTR (off-the-record) encryption.