IRC Clients for Any Platform
HexChat [Windows/Linux/Mac OS]
HexChat is a free and open source an IRC client based on XChat, but unlike XChat it’s completely free for both Windows and Unix-like systems. It runs in Windows/Linux/Unix but can be installed on MacOS with MacPorts.
HexChat DownloadsSmuxi [Windows/Linux/Unix/MacOS]
Smuxi is free and open-source, powerful, flexible, and user-friendly irc chat client that is inspired by the combination of screen and irssi. Smuxi can stay connected when you aren't and can allow multiple Smuxi frontend interfaces.
Smuxi DownloadsIrssi Linux/Windows
Irssi (pronounced like IRC) is a popular terminal-based IRC Client for Linux, it only works in Terminal and does not have an easy to use graphical user interface. It can be ran in Windows with Cygwin (but is not easy to setup).
Link to WebsiteWeeChat Linux/Unix
WeeChat is a terminal-based IRC client that's more accessible to newbies than Irssi. Everything about its interface is more intuitive than its predecessor. WeeChat's layout/interface is simpler and easier on the eyes as well.
Link to WebsiteKiwi IRC Windows/Linux/Web
KiwiIRC is a free and open source versatile Web Based IRC Client built with Vuejs, it also has Desktop Versions built with Electron so you can easily run it on Windows or Linux. There is a web server version of it as well.
Link Download/InstallLimeChat for MacOS/iOS
There aren't many free IRC clients for MacOS these days, but there is one called Limechat. You can get it from the App Store for MacOS or iPhone/iPad. There is also a paid IRC Client for Mac/iOS called "Textual".
LimeChat on App StoreColloquy for iPhone/iPad
Colloquy is an iOS IRC Client App for iPad/iPhone that costs $1.99(US). Here are more iOS IRC Apps: Igloo IRC Client (Free), Circio IRC (Free), & Palaver IRC ($1.99 USD).
Link to App StoreCoreIRC Go for Android
CoreIRC Go is a free and simple IRC Client for Android devices that customizable & easy to use. It also has a paid version for $5.99(US) if you need additional features.
Link to Goole Play