Pidgin

Adium is a free and open source instant messaging application for Mac OS X, written using Mac OS Xs Cocoa API, released under the GNU GPL and developed by the …

Miranda IM is the smaller, faster, easier instant messenger with support for multiple protocols. Designed from the ground-up to be resource efficient while still providing a rich feature set, Miranda …

Empathy is a messaging program which supports text, voice, and video chat and file transfers over many different protocols. You can tell it about your accounts on all those services …

XChat is an IRC chat program for both Linux (Open Source) and Windows (Shareware, 30-day trial). It allows you to join multiple IRC channels (chat rooms) at the same time, …

Kopete is an instant messenger supporting AIM, ICQ, MSN, Yahoo, Jabber, IRC, Gadu-Gadu, Novell GroupWise Messenger, and more. It is designed to be a flexible and extensible multi-protocol system suitable …

HexChat is a fork of XChat with bug fixes and new features.. It's free and a continuation of the XChat-WDK project.

Psi is an instant messaging application for Windows, Linux, and Mac OS X that connects to the free, open Jabber IM network (also known as XMPP). Localized versions of Psi …

emesene is a chat program that allows you to connect to different networks like MSN, Gtalk, Facebook chat, Jabber and others.

Traditionally, chat clients on the Mac have been anything but glamorous. Colloquy is an advanced IRC, SILC & ICB client which aims to fill this void. By adhering to Mac …

The goal of Gajim is to provide a full featured and easy to use Jabber client. Gajim works nicely with GNOME, but does not require it to run. It is …

Instantbird is an instant messaging client based on Mozilla XULRunner and the open source library libpurple created by the software developers of Pidgin. Instantbird is free software available under the …

KVIrc is a free portable IRC client based on the excellent Qt GUI toolkit. KVirc is being written by Szymon Stefanek and the KVIrc Development Team with the contribution of …

Konversation is an easy-to-use IRC client for novices, nut novices and experts can take advantage of its rich featureset.

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

WeeChat is a fast, light and extensible chat client. It runs on many platforms (including Linux, BSD and Mac OS). WeeChat is: - modular: a lightweight core with plugins around …

TorChat is a peer to peer instant messenger with a completely decentralized design, built on top of Tor's location hidden services, giving you extremely strong anonymity while being very easy …

Spark is an Open Source, cross-platform IM client optimized for businesses and organizations. It features built-in support for group chat, telephony integration, and strong security. It also offers a great...

KMess is the Live Messenger alternative for Linux, aiming at integration with the KDE desktop environment. With KMess, chatting with friends using Live Messenger has never been so good. Features: …

GyachE Improved (GyachI) is a fork from Gyach Enhanced Yahoo! client for Linux operating systems. This Yahoo! client supports almost all of the features you would expect to find on …

Tkabber is a Free and Open Source client for the Jabber instant messaging system. Its writen in Tcl/Tk, and works on many platforms (tested on Linux, FreeBSD, NetBSD, Solaris, MacOS …

A beautiful, free, easy-to-use chat (instant messaging) application for the XMPP protocol (Jabber, Google Talk). Project has been discontinued, though source code is still available on website

Nettalk is a powerful but easy to use free (open source) IRC-client for Windows. The smart user interface is based on Windows standards, so it is easy to get used …

FBMessenger is a stand-alone Facebook Messenger app for Linux, very similar to the official Messenger for Windows. It was created by Jack O'Connor, a Facebook Developer.

An IRC client for the Windows desktop which follows the Metro design guidelines.

Subway is a web-based IRC client with a multi-user backend and a JavaScript-heavy UI. Frontend/backend communication is done with websockets (or best available fallback where not available). The backend...