IRC

Very customizable, ZNC integration, iCloud sync ($4.99). (source) macOS

One window for multiple servers, keyboard shortcuts, fast & stable. (source) macOS iOS

Based on XChat, easy to use, spell check & multiple languages. (source) Windows macOS Linux

A simple IRC web client. (source) Web

Powerful modern IRC messenger for the web. (source, demo) Web

Uses the chrome.sockets APIs to connect directly to IRC servers without needing a proxy. (source) Chrome

Distributed (clients can attach to and detach from a central core that stays permanently online. (source) Linux macOS Windows

Multi-server/channel support, SASL support, Smooth channel scrolling / swiping. (source) Android

Focuses on making IRC less intimidating and easier to use. Web

For use in Emacs, sane defaults. Emacs

User-friendly, based on GNOME / GTK+. (source) Linux Windows macOS

Free, portable, based on Qt GUI toolkit. (source) Linux macOS Windows

User-friendly client built on the KDE Platform. (source) Linux

Simple IRC client - a terminal client in less than 250 lines of C. Linux

Terminal client, multi-protocol friendly for module authors, GPLv2. Linux macOS Cygwin BSD

Feature-full, actively maintained Android IRC client. Android

Never has a client offered such granular settings for every aspect of the IRC experience. (features, screenshots) Windows WINE

Android/Chrome OS client for power users, with ZNC built-ins, notification logic, reliable DCC, keybinds for hardware keyboards, etc. Android ChromeOS

Friendly IRC client built in Vala and GTK, designed for elementary OS. (source) Linux

An IRC client for mobile devices, from the creator of soju. Android Linux

Group chat for teams, friends, and communities. stay connected, chat from anywhere, and never miss a message (+client) (£0-£3.50/month).iOS App - Official. Objective-CAndroid App - Official. JavaNimbus - Standalone client. macOS Objective-C

Always online web IRC client. (source) Perl JavaScript Web

Most popular. many different plugins. (source) C++

Always online, lightweight and secure Open Source IRC proxying with backlogging. (source) C

Responsive, self-hosted & support for multiple users. (source, demo) JavaScript Node.js Web

A fast, light and extensible chat client. (source) Linux macOS Windows

A user-friendly IRC bouncer. Go

A simple webhook to receive SMS messages on IRC. Go

Server will allow clients to connect, join channels, change topics; basic stuff.

Modular, stable, written from scratch. (source)

Very simple and limited.

Portable and lightweight for small or private networks. (source)

Modern server that's portable and designed around specifications (bleeding-edge IRCv3 support).

IRC server without netsplits. (source)

Designed for large networks with high scalability requirements. (source)

Designed for flexibility and ease of use. (source)

Oldest IRC bot still in active development. Feature rich, uses Tcl scripting. (source) C

Tonnes of ready made features, tutorial, fully documented. (source) Python

Robust, user friendly, developer friendly. Python

Takes input from the chat and presses the corresponding key. Python

Main goals are simplicity and power. Python

Responds to configured trigger phrases with quotes from notable women. (source) Python

User-friendly and powerful. Clojure

Brainfuck

Compiles and runs C++ code snippets. C++

Simple, fast, expandable. Python

Large default plugin set, Cinch-based. Ruby

Pluggable chat bot supporting multiple protocols. Python

Extendable chat/channel/server-managenent service-providing bot. Using the Cinch Framework. Ruby

Modular, event-driven bot featuring a REST API, individual user settings and much more. (bitbot.dev) Python

Python Twisted IRC bot with a focus on ease of plugin development. Python

Python Twisted IRC bot with a focus on ease of plugin development. (source) Python

An archiving tool with an IRC interface integrated with various archiving services.

New generation LLM-powered bot with lua scripting support. Go

JavaScript

Event-based, stateful, lacking documentation. Go

The IRC adapter for hubot. JavaScript

Event-based. Go

Plugin system, simple api, arbitrary input stream, debug support. JavaScript

Event based IRC Library with a straightforward API (updated fork of PircBot). Java

Perl6 based extendable IRC client framework.

Flexible IRC bot customizable with JavaScript. C++.

Discord ↔ IRC. JavaScript

Discord ↔ IRC (with puppets) Python

Slack ↔ IRC. JavaScript

Slack ↔ IRC. Go

XMPP, Jabber, Google Talk, MSN Messenger, Yahoo! Messenger, AIM, ICQ, Twitter API, HipChat ↔ IRC. C

IRC gateway for XMPP clients C

Telegram ↔ IRC. JavaScript

Tox ↔ IRC. C

Skype (webclient API) ↔ IRC. Javascript

IRC ↔ Mattermost ↔ Discord ↔ XMPP ↔ Gitter ↔ Slack ↔ Discord ↔ Telegram ↔ etc. Go

Bouncer-style Matrix IRC bridge Python

Gateway and bridge Matrix ↔ IRC Javascript

Matterbridge ↔ IRC, Slack ↔ IRC, Mastodon ↔ IRC. Go

Searches 563 different networks.

Searches networks listed here.

Searches 318 different networks.

@Libera.Chat - Official Ubuntu support channel. (rules)

Network mostly focused on free and open source projects, run by former freenode staff.

Community of redditors and subreddits. (rules)

Community for free and open source software communities.

Privacy endorsing community serving as a safe and open space for the discussion of various topics.

Drew DeVault's Blog.

QuakeNet.

Pingdom.

Alex Williams (TechCrunch).

A vast amount of reasonably up-to-date information.

A group of IRC software authors working to enhance, improve, maintain and standardize the IRC protocol. (source)

An attempt to write an update to the original IRC protocol. documentation (source)

Lists of numerics, modes, ISUPPORT tokens and other protocol details. (source)

Collection of misc IRC protocol documentation.

Statistics around the server software in use on networks today. (source)

A CC0 set of test suites, to ensure IRC message parsers are consistent.

IRC Archives for old hard to find IRC related software.

Fast and efficient program to create statistics out of various types of chat logs. PHP Web

Convert images to halfblock ANSI or IRC, with a bunch of post-processing filters. Rust