A huge thank you to the person who wrote a review below. I've been using this extension for five years, and in the latest version, either there's an unintentional bug, or the developers intentionally introduced a leak that hadn't existed for 10 years.
This extension is currently causing a memory leak in the browser, even when I'm not opening anything and only on one page. It reaches 60 gigabytes for me, after which everything in the OS starts crashing with errors, from the browser to other programs.

I've been racking my brains for 2-3 weeks of torment, I couldn't figure out what was going on, because I've been using all the extensions for years and everything has been working without a hitch for a long time.
And it turns out that's what it is. The extension, which had been reliable for years, is now leaky and buggy, leaking 40-60 gigs of memory.
As soon as I removed this extension, everything has been fine for several weeks now.

I’ve been using LanguageTool for over 2 years and I really liked it — until about a month ago.

Recently, the extension started causing extreme RAM usage while typing. I have 32 GB of RAM, and during normal use I sit at around 18–20 GB. However, as soon as I start typing in a text field where LanguageTool is active, memory usage quickly spikes to 30–32 GB within seconds, which often leads to Firefox freezing or crashing completely.

This happens multiple times a day. In some cases, just 10–15 seconds of typing is enough to crash the browser. I even had to start writing messages in external apps (like Notepad) and then pasting them, just to avoid crashes — which completely defeats the purpose of using this extension.

What’s strange is that:
- this problem only started about a month ago,
- before that, I had zero crashes for over 2 years,
- I didn’t notice any recent updates that could explain this behaviour.

At this point, the extension has become unusable for me due to its massive resource consumption.

That said, aside from this issue, I really liked LanguageTool and I hope this gets fixed soon.

It's been getting things more wrong than right now, words that are one letter off are suggested to be completely different words or even correct words are marked as misspelled.

Sold to a US company

It was a great tool but from about 2 weeks it completely slow down my Firefox :-(

Had to remove it after about ten minutes. Even with all the "fussy" options turned off, it's just far too annoying and constantly making idiotic suggestions which if followed, would often leave meaningless sentences behind. It might be handy for people who are terrible at writing and grammar. But it was way OTT for me. I just wanted something that would underline spelling mistakes in what I was writng, to help me spot typos when proof-reading.

So maybe I'm noy the target audience.

I was also not happy with the thought of everything I write on the web being sent off to be checked. Even if [as is always the case] the developers claim everything is very secure and encrypted... yadda yadda.

Neither did I like the fact that a lot of the functionality has to be paid for. Not something that was mantioned anywhere in the blurb, as far as I could see.

This WAS! The best spell checker for the web BUT NOW it is going behind a pay wall sorry but I can NO longer recommend this tool to use

I bought the premium bull..... and since then it went all down the drain.... After 30 minutes of work it slows down the browser like I would work on my toaster but I really have a high high end PC for Gaming and Development

I understand that the company needs to make money from its work, however wanting 20 € per MONTH for a grammar checker is insane to me. Harper is also open source and free, I switched to that. 20 € per year would be cool, but 240 € is a hard pass. :(

in 14 days the extension will be premium only and they except you to pay 20 USD a month for this extension


"how many times do we need to teach you this lesson old man?"

Absolutely no warning. They disable and remove the extension saying you must pay for it now. I go to check the pricing...$20.00 a MONTH!!!!! Are you insane. Grammarly is hundreds of times better and it's only $12.99 a month. Can you say the word bankruptcy! The employees of LanguageTool...time to go looking for a new job! Oh...and get this. The announcement says you must pay for it now. You click on it and it says it's $24.99 a month. You go directly to the site and it's $19.99 a month. They are charging an addition $5.00 to the people that have used their product for years. They did EVERYTHING wrong. No coupons on saying thanks for using our product. A discount for saying, hey, we get this comes as a surprise. This should help for a few months. Instead, they charge the users MORE!!!!

Opened download file and it was some map quest app or something.

Does not save or sync with the dictionary. The AI they have to help is a moron.

Prioritizing greed over It's long time users, or this just your bait‑and‑switch, Either way you've lost me and you should also be removed from Firefox recommended list.

La aplicacion ahora te obliga a pagar para su uso, denunciar y desinstalar.

Totaler Mist was jetzt abläuft das man dafür bezahlen muss. Lasst doch die Leute bezahlen wenn sie zusätzliche KI Dienste haben wollen. Ich brauche das nicht aus diesem Grunde habe ich diese Erweiterung aus meinem Slimjet Browser (Chrome basiert) deinstalliert. Ich brauche nur Rechtschreibprüfung und Grammatikprüfung. Aus diesem sehe ich nicht ein extra zu zahlen für KI Dienste. Das eure Schwesterfirma eine kostenlose Alternative bereit hält ist gelogen. Wenn es auch in Firefox passiert werden ich die Die Rechtschreibprüfung und die Grammatikprüfung in Open Office machen. Ich arbeite dann mit Copy and Paste.

It's announced that the whole extension is going to be locked behind the Premium subscription. While I understand the need to make money, the costs are not reasonable for me and my usage. I also don't like your explanation that this is because of the rising costs of the AI-features, which I didn't need nor was convinced of to begin with.

You can circumvent this (for now?) if you set up your own server, but I think I prefer to part ways at this point.

Really used to love this until it started using gen AI more and more and kept finding more errors in its checks.

Just like grammarly pushing the premium very hard. I'm not going to pay for this.