Trillian is a proprietary multiprotocol instant messaging application created by Cerulean Studios.

It is currently available for Microsoft Windows, macOS, Linux, Android, iOS, BlackBerry OS, and the Web.

It can connect to multiple IM services, such as AIM, Bonjour, Facebook Messenger, Google Talk (Hangouts), IRC, XMPP (Jabber), VZ, and Yahoo!

Trillian no longer supports Windows Live Messenger or Skype as these services have combined and Microsoft chose to discontinue Skypekit that was used for connection.

Initially released July 1, 2000, as a freeware IRC client, the first commercial version (Trillian Pro 1.0) was published on September 10, 2002.

The program was named after Trillian, a fictional character in The Hitchhiker's Guide to the Galaxy by Douglas Adams.

[8] A previous version of the official web site even had a tribute to Douglas Adams on its front page.

Prior versions used the corporate logos for each service, but these were removed to avoid copyright issues, although some skins still use the original icons.

XML-based history makes the log easy to manipulate, searchable and extendable for future functions.

[12] Trillian Pro also has a stream manipulation feature labelled 'time travel', which allows the user to record, and subsequently review, pause, rewind, and fast forward live video and audio sessions.

According to Cerulean Studios, the makers of Trillian, SecureIM enciphers messages with 128-bit Blowfish encryption.

When users point their mouse over the word, the lead paragraph of the corresponding article is downloaded from Wikipedia and displayed on screen as a tooltip.

[16] Trillian also came with an easier skinning language, Stixe, which is essentially a set of XML Entities that simplifies repetitive codes and allows skinners to share XML and graphics in the form of emoticon packs, sound packs and interfaces.

Plugins by Cerulean Studios itself include spell-check, weather monitor, a mini-browser (for viewing AIM profiles), Winamp song title scroller, stock exchange monitor, RSS feedreader, and conversation abilities for the Logitech G15 keyboard, as well as a plug-in for the XMPP and Bonjour networks.

Plugins are available for free and are hosted on the official web site, but most need Trillian Pro 2+ to run.

After several internal builds, the first ever public release of Trillian, version 0.50, was available on July 1, 2000, and was designed to be an IRC client.

The new version implemented file transfer in all IM services, a feature most requested by the community at the time.

It used the contact list as the main window (as opposed to a status window 'container' in prior versions) and featured a brand new default skin, Trillian Cordillera, and an emoticon set boasting over 100 emoticons, setting a record apart from other messengers available at that time.

It supported AIM group chats and was the first major IM client which included the ability to encrypt messages with SecureIM.

Trillian received coverage and favorable reviews from mainstream media worldwide, particularly by CNET, Wired and BetaNews.

[19] Trillian appeared in the Jupiter Media Metrix Internet audience ratings in February 2002 with 344,000 unique users, and grew to 610,000 by April 2002.

Messenger webcam support, pop-up e-mail alerts and new plug-ins to shuttle news, weather and stock quotes directly to buddy lists.

It appeared Trillian Pro would be marketed to corporate clients looking to keep in touch with suppliers or customers via a secured, interoperable IM network, and a relatively stern user interface.

attempted to block Trillian from connecting to its service[23] in their "efforts to implement preventative measures to protect our users from potential spammers."

The Trillian developers assisted its open-source cross-platform rival Gaim in solving the Yahoo!

Sean Egan, the developer of Gaim, posted in its site, "Our friends over at Cerulean Studios managed to break my speed record at cracking Yahoo!

However, it appeared that Cerulean Studios worked with Microsoft[26] to resolve the issue on August 2, 2003, long before the deadline.

After months of beta-testing, the final build of Trillian 3 was released on December 18, 2004, with features such as new video and audio chat abilities throughout AIM, MSN Messenger and Yahoo!

The name for version 4, Astra, is the nickname used by the same fictional character that is the namesake of the software, which is a reference to The Hitchhiker's Guide to the Galaxy.

On July 3, 2009, Cerulean Studios reopened the premium web version of Astra to public testing.