Blocks more than it says it will.
Even blocks appropriate sites and the ability to uninstall it which is against FF ad-on policy.

Hello, I'm currently testing parental control systems to see which adult content tagging systems they respect. Even with "Examine Meta Content" turned on in the sensitivity settings, this extension fails to block websites based on various meta tags used by adult websites to identify themselves as such.
I've tested the following meta tags in use by adult websites and none of them cause the page to be blocked:
<meta name="rating" content="adult" />
<meta name="rating" content="mature" />
<meta name="RATING" content="RTA-5042-1996-1400-1577-RTA" />
<meta name="rating" content="RTA-5042-1996-1400-1577-RTA" />

This let me access at least two websites and various twitter accounts with explicit pornographic content which would otherwise have been blocked.

Also, all adult sites I've checked so far include at least one of these tags.

Don't waste your time, the password protection feature is behind a paywall.

A bloquer l'accès à des sites pour faire les devoirs de mes enfants. Demande de payer pour débloquer le site. Extension à fuir.

Password protects only the browser settings. It can easily be deactivated or removed from the puzzle icon - even with a password in place

Works, but uses the shady practice of not being able to set a password unless you pay them, so even if it's there, anybody can just turn it off anyway
Edit: Even if you pay them, trying to install the android version says not intended for android,wtf??

Awful add-on. There is no way to get rid of it and never blocks the right things. For example, once it blocked the word 'Essex' and multiple other times it blocked the word 'adults' in the sentence 'kids and adults alike will love this'.

Whenever an 'alert' pops up, it automatically switches all of your tabs to the website that it thought was 'dangerous'. Interrupted my workflow way too many times!

All filtering features are most certainly not free. You must pay to make an account to change any of them.

Useless even as a personal accountability tool, as the "fReE" version blocks non-adult websites for no reason.

I had this extension downloaded for less than 48 hours before I had to delete it.

So, in order to prevent my child from turning off this add-on, I have to put a password. In order to put a password, I have to pay.

I get that it's a great tool, and you're providing it for free, but it's kind of useless when the whole of it can be undone by a kid with enough time to poke around in the settings.

Thanks, but no thanks.

It was difficult to set up and difficult to remove. It filtered strange things, like the number 18. Why??!!! Yet some very filthy material came up several times.