ChatZilla: Powerful IRC Client for Firefox
ChatZilla is an IRC client built as a Firefox add-on and providing enough features to use it just like any other standalone IRC client. ChatZilla will fit best as an IRC client when you don't want to use a separate application for getting on IRC.
The interface resembles the classic user list and chat window appearance, making it intuitive and using the usual Firefox shortcuts for common tasks like switching tabs or closing the current chat window.
The first time it starts, ChatZilla will offer the basic information to start using it, like the needed commands to get help, links to get started with IRC, a FAQ and links to connect directly to one of the many popular networks like Freenode, QuakeNet, EFNet, IRCNet, Dalnet or Undernet.