HexChat is a fork of XChat.
Ranked in these QuestionsQuestion Ranking
Pro Free and open source
Pro Simple, clear interface
HexChat's default interface is clear, well-organized and intuitive. Channels can be laid out as both tabs and in a tree structure. All components such as user lists, topics bar or even menu bar can be hidden to provide a clean way to interact. Conversely the interface can be configured to show quick access buttons for changing channel flags, sending files or performing operator actions.
Pro Functionality can be extended with plugins and scripts
HexChat has a great list of plugins and scripts and is compatible with most XChat plugins. XChats library is incredibly extensive. There is a wide range of both useful and fun plugins. It's possible to add an RSS feed, play a game of chess or control an mp3 player via chat while translating everything written to l33t speek.
Pro Highly scriptable
HexChat supports scripting in Perl and Python. Both languages can be used to extend functionality of the software - bots can be written, automation can be added, new dialogs can be created.
Pro Highly customizable look
While most clients allow changing the theme or style of a window, HexChat gives complete control over what it looks like. It's possible to set a custom image as the background, changing font, or syntax colors.
Pro Works for any level of user
HexChat is an advanced IRC client that is good for beginners as well as those users who like to get under the hood. It is easy to get up and running, but has all the advanced features that a power user would need.
Pro Actively developed
Pro Available in multiple languages
Con Bad character support
Con High CPU usage on some Windows 8.1 & 10 versions
HexChat has a long-standing unresolved issue with high CPU usage spikes on key-presses that is noticed in some Windows 8.1 and 10 versions.
Con Poor High DPI Display Support
Text is blurry and hard to read on HDPI displays. Both in Windows and Mac.
Con Not actively developed
Development is pretty much halted on this. No major update in 2 years. Outdated features/functions. It's still using gtk2 when gtk3 is available. Using xtext instead of gtkTextView.