Furaffinity Notifier от DASPRiD

Furaffinity notifier is a small add-on which places an icon in your browser to notify you when you have not notifications on furaffinity.net.

It checks for new notifications in a configured interval (5 minutes by default) and will display a badge number on the icon to indicate new notifications. By clicking on the icon, you get a summary of which types of notifications are available and a click on each type will take you directly to the corresponding sub-page on Fur Affinity.

In the add-on options you can specify how often the website should be checked and which types of notifications you are interested in.