ircII (pronounced i-r-c-two, and sometimes referred to as IRC client, second edition) is a free, open-source Unix IRC and ICB client written in C. Initially released in the late 1980s, it is the oldest IRC client still maintained. Several other UNIX IRC clients, including BitchX, EPIC, and ScrollZ, were originally forks of ircII. For some, ircII set the standard of quality for IRC clients, however other clients have since overtaken ircII in terms of popularity. The application has been promoted as being "fast, stable, lightweight, portable, and easily backgrounded".
ircII runs in a text-only shell-based environment. The application has no menus, pop-ups, or any other GUI features or support for CTCP SOUND that many graphical IRC clients, such as xChat typically have.
ircII was the first IRC client to implement Client-to-client protocol (CTCP) and the Direct Client-to-Client (DCC) protocol, and was the first client to implement file transfer capabilities over IRC. The CTCP protocol was implemented by Michael Sandrof in 1990 for version 2.1. The DCC protocol was implemented by Troy Rollo in 1991 for version 2.1.2, but was never intended to be portable to other IRC clients.