This is one of the most underrated addons here and it must be included in Firefox as native solution for horrible multi language spellchecking they currently have.

Oh my god this works so damn well! I have been so annoyed by constantly having to manually switch between spell-check languages for so long, but never found this add-on before.

Thanks so much for this great Add-On Jacob! :-)

Very useful add-on.
Thanks.

thank you

I had to restart FF v68 two times and play with spell checking languages manually until it finally switched automatically in Gmail ! Working fine so far :-) Thanks !

After just a few testing, it looks like it works fine.