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

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

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

Kopete is a multi-protocol, free software instant messaging client released as part of the KDE Software Compilation. Although it can run in numerous environme…

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

iMessage is an instant messaging service.

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

Trillian is a proprietary multiprotocol instant messaging application.

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

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

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

Tkabber is a GPL instant messaging client for the XMPP protocol which uses the Tk toolkit for the GUI.