They say it works on almost any web site, just not the ones I use. I'm not sure where all of the 5-star reviews come from, but I found it uninspiring and not useful.

Not a fan of "AI" part, I just wanted a single word spelling checker, absolutely don't need any of the other features :/

Terribly clunky and giving some of the worst grammar suggestions turning my sentences into broken Engrish

I just want a good spellchecker that quickly helps fix words, not this mess

Made my performance horrible. Turning it off fixed the issue immediately.

AI

Cannot detect Romanian language, shame! Also to send all the information to your data base. No thank you and adios!

Yet more AI garbage. Go away and leave me alone forever, please and thank you.

It no longer works with Google Docs (I get spelling error underlines but it doesn't allow me to click on them).
They also keep pushing gen AI features.

Will record your personal info including bank info and passwords very sketchy and dangerous! Total garbage I can manage far batter than this joke of an add on. I tried it out just in case I missed something and it cost me more time trying to stop all the mistakes it made! I'd leave out a letter like say "leter" and it would give me all the choices except "LETTER"! As for so called reviews claiming the premium is great I wonder how much they were paid or do they work for the joke of a company. This is by far the worse add-on I've ever tried. It's non-stop so called mistakes aren't mistakes like " it will point it out for no reason and the user is left with a bunch of nonsense. Avoid this you'll do better on your own and will save yourself time on correcting their mistakes. As for the 5 star reviews yeah right!

You get notified of certain errors only checked by having a premium subscription, but it won't tell you where or what the errors are and you can't disable this incredibly annoying behavior. Also, despite the fact that there's no mention of AI in the description, AI integration is all over it (and very limited for free users). Even the name of the extension in the Add-On Manager has AI in it. It's the very first word! What a weird, shady-seeming, and obnoxious extension.
And by the way, LanguageTool, your setup process has at least two typos in it. You can't even be bothered to run your own copy through the AI tools you try to push on us? You failed to inspire confidence from the very beginning and then you lived up to that impression spectacularly.

Es zeigt die ganze Zeit es wären noch mehr fehler vorhanden, aber nicht wo sie sein sollen.

Per its new privacy policy, the addon now records and sends all writing back to its data centres allowing LanguageTool admins to read through.

Intrusive, overblown and constantly nagging about an upgrade many can't afford. Don't need something as complicated as this.

Поки що безтолкове доповнення, бо не підтримує чеську мову...

LT requires the following permission: Access your data for all websites. According to Firefox support the permission allows LT to "read the content of any web page you visit, as well as data you enter into those web pages, such as usernames and passwords" That is too much risk to give to a spelling and grammar checker

This addon is great but only works for first 20 words in the day, is trash need buy a pro version for this trash

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.

They can see everything you write, and they record that unencrypted data. I should never have even tried this.

Has become very stupid. Makes incorrect "corrections" constantly, gets tense wrong, does not know words exist (it tried to correct 'withering' to 'dithering' for no reason). Used it for a while but have had to stop because it's irritating more than helping.

The amount of times it suggests changing the tense to be incorrect is staggering. Sometimes I will accept its suggestion, then it immediately changes its mind and suggests I undo its suggestion. It also strongly suggests breaking sentences up to be grammatically incorrect. It is consistently dumb and only gets it right 50% of the time. I can't recommend it.

Breaks spell checking completely, now nothing is being spell check at all!

Not a very smart spell checker.