None of the mozilla extensions and addons from "https://addons.mozilla.org/en-US/firefox/language-tools/" doesnt a job of being in 2019. Their database are 20 years old where they dont know the word Flipboard which they say is clipboard. SERIOUSLY. None of the english lang or dict works like they are productive friendly for someone working in 21st century where words update daily and social media has changed the words we never thought existed. It doesnt know the word awesomesauce until it is corrected to awesomeness. Most importantly it doesnt detect words from other language that have taken place in English dic like it detects "Laddu or laddoo" as "lad do". LEARN FROM CHROME WHERE IT HAS OPTION TO LEARN FROM GOOGLE FOR SUGGESTIONS. WHERE'S YOURS?

GO FOR BETTER DICTIONARIES PRESENT ONLINE - https://www.lifehack.org/articles/productivity/the-best-10-online-dictionaries.html

Fabulous, now I can pretty much ditch my Chromium based browser. Firefox has Picture-in-picture (off by default!) and a Spell-checker... Who would have known 😱

This is an essential part of using Firefox, why the hell do Mozilla not just include it in the UK version, it comes with NO ability to spell check, but the US one has the US spell checker which for us in England is rubbish - get a grip Mozilla, and add spell checkers for all nations not just bloody America!
Thanks Marco for doing their work for them ;)

Works perfectly.
I had to remove my installed version of Firefox as I had installed the US English version (who knew!) and the US English version seems to default to US English and will not allow you to select UK English as it's default.

Following reinstallation I installed the first English Dictionary in the Add-on list and it simply does not work.

Having uninstalled that one and installed this one, I am pleased to report a now functional UK dictionary. Bravo!

I find this ENGLISH english (not US) spellchecker brilliant. The only things it misses are homophones where I use the wrong spelling but that spelling is valid for another context e.g. great and grate . . . but no system can be expected to cover that!! I also like the way it works even when I'm filling in forms etc.

Sehr gut