Tab Icon Badge от bruxis

Updates the favicon shown by a given tab by overlaying a small numeric badge to show the "unread count" (number in parenthesis in the page title).

Unfortunately the only way to do this within an extension today is to draw a new favicon with the badge over it. Since the icon is small, the badge must also be relatively small. You can change the font size, color, and position of the badge, among other settings, in the addon options page.

This extension is heavily inspired by "Tab Badge" which predates it.

FYI: For userChrome.css users, there may be promising opportunities to increase the favicon size when using the option to reduce the original favicon size when a badge is overlayed on it (e.g. increase by 25% when using the 80% size reduction).