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

Trillian is a proprietary multiprotocol instant messaging application.

ICQ is an open source instant messaging software.

Demonsaw is a secure, anonymous, free, and decentralized x-platform information-sharing application with end-to-end encryption and no client P2P.

WhatsApp Messenger is an instant messaging platform owned by Facebook.

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

Ring (SFLphone) is an open-source SIP-compatible softphone and instant messenger for Linux, Microsoft Windows, OS X and Android.

Matrix is an open protocol for real-time communication. It is designed to allow users with accounts at one communications service provider to communicate with…

Dialog Messenger is a handy and feature-rich enterprise multi-device messenger available for server or cloud.