Good and useful extension, but lately it shows the alt text tooltip on many (but not all) images regardless of whether that behavior is toggled on or off. Restarting Firefox doesn't alter that, nor does disabling and re-enabling the extension.

very good add-on, it's great to have options ! I thought of two things that could be great to add : a button in the pop-up to just toggle the whole thing on or off, and an option to copy the alt text to the clipboard (maybe in the right-click context menu)