Irssi

Irssi is a terminal-based IRC client for Unix-like systems. Written in C, it is designed to run inside text terminals and can be accessed via screen, tmux, or direct console sessions. Irssi was created by Timo Sirainen and has been maintained by a community of contributors. The project is licensed under the GNU General Public License (GPL) v2 or later.

Irssi emphasizes a lightweight, stable core with extensive extensibility. It supports multiple servers and networks, persistent chat buffers, and a configurable, color-coded user interface suitable for fast, keyboard-driven workflows. The client provides features such as TLS/SSL encryption, SASL authentication, DCC and CTCP support, and flexible message logging. Its modular design allows users to tailor the experience through scripts and themes.

Extensibility is a central feature. Irssi can be extended with scripts written in Perl, and a large ecosystem of scripts is available to add functionality such as automation, custom commands, or enhanced formatting. Script loading is dynamic, enabling users to customize behavior without rebuilding the client. The user community also contributes themes to change the appearance of the chat windows and UI.

Historically, Irssi gained popularity in the early 2000s as a robust alternative to graphical clients, especially on servers and in environments without graphical desktops. It remains widely used among users who prefer a non-GUI IRC client and who value scripting and reliability.