This add-on sets the default client for opening IRC links using protocol_handlers.

Whenever a link using the IRC protocol is clicked, the link is opened in the URI defined in the add-on's manifest. In this example, all IRC protocol links are opened in mibbit.com.
For example, once you've installed the extension, click this link irc://irc.freenode.net/drupal and the protocol handler opens the Drupal channel in mibbit.com.

How to use protocol handlers to pass content to an application or website designed to handle that content.