Not very good and over-complicatef

I meant complicated of course but this rubbish app didn't pot th error

If I can't install a different spell-checker on Firefox I'm going to use a different browser, that will be a shame.

Edited to add: Despite the Developer's response my opinion stands that this add-on is useless. Fortunately I have found an alternative that works perfectly.

The extension is no longer open source.

Некорректно определяет исходный язык.

A free spell checker now charges for spell checking! They highlight misspelled words, but you'll have to go to a search engine to find the correct spelling yourself; no, I'll find another spell checker!

NOTE:
The developer responded, "That's not true." I know my experience, but the popup bubble always says Basic Account and offers no corrections! Every single time, I had to go to duckduckgo.com to find the correct spelling. If Language Tool has decided to back off it's irritating policy, I don't know because I'm no longer using them.

A closed-source extension that is asking for access to all my data from all websites is a privacy nightmare. It's also a huge disappointment, as the add-on used to be open-source.

Was a privacy oriented, EU hosted, well rounded and good looking spell checker that is now US based, AI filled, and pay to use.

Не всегда правильно подставляет запятые

It does not work with the Bulgarian language. It recognizes it as Russian. You have an option for Bulgarian but it does not work.

No clear instructions for adding this add on to a android Firefox browser. Can't do a thing with it.

It misses many basic grammar errors. I also don't like the message "we found 'issues' but pay to find out what they are" can't be turned off.

Since you have decided to go subscription mode...
1 STAR.
Understand that people are exhausted and tired of paying every month for things. It's over. There are other alternatives. I get it. You should be paid for your efforts. But let us pay once, and be done with it.

While it is working in normal circumstances, this addon breaks eBay! When listing new item for sale, eBay form is blocked from working, and typed formatted text does not translate to HTML and item description remains empty. This breaks even existing eBay listings, when you click to edit a listing, click text field, description is completely gone, submitting listing with changes will cause entire text gone! Please be careful when working with big text fields, this addon is not compatible with everything!

Typed a few sentences, it corrected a few errors, then told me I needed to pay for premium to detect any further errors.

Premium might be worth it for some people, but for me it's not that serious. I can live with the occasional grammar mistake.

Não está funcionando no Firefox. Utilizo essa extensão em todos os navegadores que uso a anos, é a melhor.
Mas infelizmente no Firefox ela não funciona em nenhum campo ou documento de texto.

Not much use, doesn't detect grammar issues and has very limited options for guessing what you were trying to type. Turned it off almost immediately.