Google Talk is a web-based application which allows users to have a combination of voice over IP and instant messaging functionality. The application is free to use but the software behind the application itself is proprietary to Google.

The instant messaging component of Google Talk utilizes an open protocol known as Jabber. The messaging functions may be accessed by client servers that do not belong to Google. The application is supported on Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows 7, as well as Mac systems running from Intel processors.http://www.bigblueball.com/im/googletalk/

A mobile version of Google Talk is also available for smartphones. Specific clients for BlackBerry, iPhone, Palm and Android based systems exist. Other cellular phone models using different operating platforms can access Google Talk through Adobe Flash Player.http://www.bigblueball.com/im/googletalk/

Google Talk communications are normally encrypted from client to server, but in certain circumstances,such as when accessing a Google talk server from a non-US client, the connection may be unencrypted.

Voice mail was integrated into the Google Talk application in 2006. The voicemail function allows for messages up to 10 minutes in duration to be stored in MP3 format. These messages can then be downloaded as MP3 files or listened to via Gmail and its MP3 applet.

Offline messaging capability was also incorporated in Google Talk in 2006. This allows for messages to be left on a user's account even if they are offline, with the message appearing when the user signs on to the service.