Useful for multi-lingual users Noté 4 sur 5 étoiles
This add-on allows to quickly switch between the various installed spell-checking dictionaries.
In my case, I often type English or French messages, and Firefox chooses the language depending on the settings of the site, which sometime are incorrect or just not suited to the moment.
Dictionary Switcher is able to detect what language you use after a few words (probably trying the dictionary raising the fewest errors...) and if that's not enough, it allows to set it by a single left click on the toolbar icon (going to the next language, good if you have few dictionaries) or a right-click (showing a menu to choose quickly what you need).
It doesn't seem much, but it saves time when you have a big context menu and you search the Language item, then select the right one.
Side note: it can also be useful when you want to use the same dialect than the one used in the site you are, ie. if you have, for example, installed British, Australian and US dictionaries, or in French classical French vs. reformed one.