Not bad but it cannot spell Bisglycinate or Allulose, Magnesium Bisglycinate from Magnesium and Allulose the natural sweetener.

What else can the AI not spell? That's why I took some stars off, because it cannot learn words, or slang talk.

Edit-

I just found out this cannot spell check for a paragraph that exceeds a certain amount of words, it's a lot but it has a limit, on the other side of why I don't like this addon anymore is it no longer supports windows 7, as I have updated my firefox on windows 7 this app says an updated version of firefox is needed for this extension.

I think it's a nice try for small spelling check, if you let us program it and say add word to dictionary maybe it can learn slang?

Also maybe a version that can support Windows 7 firefox version? I've had to rip the stars away because I can no longer use it updated.