Alternatives to Atomic IRC for all platforms with any license

Pidgin

Pidgin is an easy to use, multi-protocol chat client client used by millions. Connect to AIM, MSN, Yahoo, XMPP, and more chat networks all at once. It has built-in...

Free Open Source Mac Windows Linux BSD PortableApps.com ... Xfce
Support for Multiple protocols Support for Multiple protocols Supports XMPP Extensible by Plugins/Extensions ... IRC Plugins Messaging Multiple languages Multiple Account support Multiple chat protocols Portable Video calling Voice Call Xmpp Add a feature

1479 Like
HexChat

HexChat is an IRC client based on XChat for Linux , but unlike XChat it’s completely free for both Windows and Unix-like systems. HexChat was...

Free Open Source Mac Windows Linux BSD PortableApps.com ... Xfce MacPorts XQuartz
IRC Portable Add a feature

199 Like
Trillian

Trillian is an instant messaging app that works on phones, tablets, and desktops while keeping your chats neatly synchronized between all of them! We think conversation...

Freemium Mac Windows Linux Web Android ... iPhone Blackberry iPad
Facebook integration IRC Messaging Support for Multiple protocols ... POP3 Support Team Collaboration Xmpp Add a feature

275 Like
Adium

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 Adium...

Free Open Source Mac
Support for Multiple protocols Xmpp Customizable Messaging ... Multiple languages OTR Supports XMPP Tabbed interface Support for Themes Add a feature

334 Like
irssi

Irssi is a terminal based IRC client for UNIX systems. It also supports SILC and ICB protocols via plugins.

Free Open Source Mac Windows Linux BSD Cygwin
No features added Add a feature

79 Like
mIRC

mIRC is a popular Internet Relay Chat client used by millions of people, and thousands of organizations, to communicate, share, play and work with each other on IRC...

Commercial $ $ $ Windows
Colored Text IRC Add a feature

88 Like
Quassel IRC

Quassel IRC is a modern, cross-platform, distributed IRC client based on the Qt4 framework. Distributed means that one (or multiple) client(s) can attach to and detach...

Free Open Source Mac Windows Linux Self-Hosted
IRC QT Based Standalone Add a feature

46 Like
XChat for Linux

XChat is an IRC chat program for both Linux and Windows. It allows you to join multiple IRC channels (chat rooms) at the same time, talk publicly, private one-on-one...
- Discontinued
  The program is no longer updated. Last version, 2.8.8, released in May 2010, can be still downloaded from the official website.
Free Open Source Windows Linux
IRC Add a feature

102 Like
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WeeChat

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...

Free Open Source Mac Linux Android BSD Xfce
Command line interface Extensible by Plugins/Extensions IRC Modular System ... Support for Multiple protocols Xmpp Add a feature

32 Like
KVIrc

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...

Free Open Source Mac Windows Linux BSD PortableApps.com
IRC Portable Add a feature

40 Like