Trillian is a multi protocol instant messaging application for Windows created by Cerulean Studios that can connect to multiple IM programs from one client, such as AIM, ICQ, MSN Messenger, Yahoo! Messenger, IRC, Novell GroupWise Messenger, Bonjour, and Jabber and Skype networks (the latter four with Trillian Pro which allows for additional plug-ins).

Initially released July 1, 2000 as a freeware IRC client, the first commercial version (Trillian Pro 1.0) was published on September 10, 2002. Trillian's creators have promised to continue to support and maintain a free version of Trillian, and it will remain a closed-source application.

Trillian Features:

• Trillian connects to multiple instant messaging services without the need of running multiple clients
• Trillian Basic and Pro both come with Activity History, and both log the history as both plain text files and as XML-files.
• Trillian Pro also has the so-called Time Travel feature, allowing the user to record, and subsequently review, pause, rewind and fast forward live video and audio sessions.
• Trillian has its own unique skinning engine known as SkinXML. Many skins have been developed for Trillian
• Trillian is a closed-source application, but the Pro version can be extended by plugins.
• Users can purchase Trillian for $25. Extending "membership" to download a major release upgrade is an additional $5.