Rated 5 out of 5 stars

While using it a few seconds ago I came up with this idea/suggestion:

Is there a way you could consider adding the feature of having Font Finder detect if the font being rendered is coming from the @font-face declaration in the CSS (or which CSS if you have several CSS files) or if it's coming from your local font folder?

The thing is that in order to troubleshoot font rendering issues sometimes one needs to test if the @font-face (or web font service for that matter) is actually working, or if the font rendered is being pulled from the local /fonts folder.

Thanks for such great extension.

This review is for a previous version of the add-on (1.0.1-signed). 

Although that's a great idea, currently Firefox's code isolates us from knowing the true source of the font and makes a font-face declaration indistinguishable between any web-font or locally loaded font.

As soon as that capability becomes available within Firefox, we'll quickly add it to FontFinder.