It doesn't work. The spelling always defaults to US English. If I had to rely on a spell-checking browser, I'd use Chrome or Edge!

English (GB) unavailable as an option for spell checking. Only English US. Using FF97

Does not work, not now, not ever.

Uses American Spellings not English.

Language settings in Firefox is a complete mess.

Does work but sometimes you need to google a bit

Firefox will not use it and states only US pack available for my locale. So uses US spellings. I want to use British English!

Completely overridden by the standard issue US English that cannot and will not let me replace it with the correct English for my locale, UK.

ca ne marche pas

Says it's installed but it simply doesn't work. Spell check still marks UK spellings as wrong.

no matter WHAT i do, firefox ALWAYS resorts to USA spelling.

Quite incomplete but better than anything else free out there & I appreciate this author's maintenance over the years.