Top Alternatives to Trillian

Pidgin is a free and open-source chat client which supports AIM, Google Talk, ICQ, XMPP protocols.

Adium is an Open source multi-protocol instant messaging client for Mac OS X, supports MSN, Jabber, Yahoo! and other networks.

Tox is a peer-to-peer instant-messaging and video-calling protocol that offers end-to-end encryption.

Signal is the most scalable encryption tool.

Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application.

Digsby provides you with IM, email and Social networks in one easy to use application.

Miranda IM is an open source multiprotocol instant messaging application, designed for Microsoft Windows.

Empathy is an instant messaging (IM) and voice over IP (VoIP) client which supports text, voice, video, file transfers, and inter-application communication over various IM protocols.

Glip is fully searchable, real-time group chat; video chat, task management, file sharing app.

IM+ supports simultaneously major IM services, including Google Talk, Twitter DMs, Yahoo!, AIM/iChat, ICQ, Jabber (and Slack through Jabber), etc.

Kopete is a multi-protocol, free software instant messaging client released as part of the KDE Software Compilation. Although it can run in numerous environments, it was designed for and integrates with the KDE Plasma Workspaces.

ICQ is an open source instant messaging software.

Gajim is an instant messaging client for the XMPP protocol which uses the GTK+ toolkit.

Miranda NG is a successor of Miranda IM, a popular multi-protocol instant messaging client for Windows.

Quassel IRC, or Quassel, is a graphical, distributed, cross-platform IRC client.

Instantbird is a cross-platform instant messaging client based on Mozillas XULRunner and the open source library libpurple used in Pidgin.

iMessage is an instant messaging service.

Xabber (XMPP and Jabber) is a XMPP client for the Android Operating System.

Apache Spark is an open-source cluster-computing framework.

KakaoTalk (Korean: 카카오톡), or sometimes KaTalk, is a free mobile instant messaging application for smartphones with free text and free call features.

Psi is a cross-platform powerful XMPP/Jabber client (Qt, C++) designed for the Jabber power users. Psi+ is a development branch of Psi IM XMPP/Jabber client.

Conversations is an open source XMPP/Jabber client for the Android platform.

Rambox is a free and Open Source messaging and emailing app that combines common web applications into one.

Tencent QQ (QQ) is an instant messaging software service.

Finch is a console-based IM program that lets you sign on to AIM, Jabber, MSN, Yahoo!, and other IM networks. It runs on Unixes. It uses GLib and ncurses.

Bit Chat is a secure, peer-to-peer, open source instant messenger with end-to-end encryption.

Coccinella is a free and open-source cross-platform client for the XMPP/Jabber-instant messaging-protocol.

Zulip is a chat and collaborative software.

Disa is your new messaging hub. Conversations from different services can seamlessly be joined together, or disbanded within seconds.

Dasher Messenger provids a way to message friends.

YakYak is a desktop chat client for Google Hangouts.