It does not block any site. It does nothing when you add the URL to sites to block. Zero Stars

Trash, doesn't even block websites

It wasn't created with the user in mind. The usability is terrible, the configuration page is counter-intuitive. It's as if somebody actively tried to make it as bad as possible. It doesn't have to be like that...

INUTILE extension !
On peut facilement Activer ou Désactiver l'extension avec le bouton même si le compte n'est pas connecté.
Un enfant de 10 ans saurait le faire.
Donc cette extension ne sert à rien !!

USELESS extension!
One can easily Enable or Disable the extension with the button even if the account is not logged in.
A 10 year old child could do it.
So this extension is useless!!

¡Extensión INÚTIL!
Se puede habilitar o deshabilitar fácilmente la extensión con el botón incluso si la cuenta no ha iniciado sesión.
Un niño de 10 años podría hacerlo.
¡¡Entonces esta extensión es inútil!!

This extension rendered FF completely unusable. Had to restore a profile backup.
As soon as I added a site to the block list and saved settings, FF created several hundred new processes, consumed 20GB of memory, freezing itself and the system. Tried to kill the process and then start FF again - same thing happens on start, hundreds of processes, all RAM consumed, etc.
Avoid.

Pointless. Blocks pages, but replaces blocked page with one of it's own. So still getting unwanted pages!!!! Pointless add on.

Not only is setting custom rules inordinately difficult, but when I added a new rule, following the documentation, it blocked and overwrote every single tab I had open, (none of which had anything to do with the content of the rule I had written, most of them minimized). Seemingly arbitrarily, this add-on rarely preserves the URL of the site it had just blocked, making it essentially impossible to meaningfully recover anything.
The detour of trying to scan through my history, retracing links and searches to figure out which tabs were for which project and reorganize them is not something that I wanted to do, especially with nothing to show for it.

Can't be used to block only the main page of a specific site without extensive workarounds or knowledge of coding.

Scheduled unblocking no longer works.

I love this add-on but the update of 2 days ago seems to have broken some important functionality. When I enter my master password to unblock a site temporarily (such as YouTube, for school or work), I receive "An unexpected error occurred" and I cannot properly unblock any sites. I must disable the extension for the time being. Please update ASAP.

this would be great if the "Schedule Unblocking" option made any goddamn sense.

doesn't work

Not sure why Firefox recommends this extension that completely fails to work. Only blocks one site, and only after programming it twice. Terrible interface. Blocking hours very confusing. Gets the information by asking what time you want things 'unblocked' first. My advice to Ray would be eliminate the "unblocking" part. Just focus on what times people want things blocked. Very confusing when you ask "what time do you want things unblocked?" Get rid of the "generate unblocking hours automatically," if you need it, that should be behind the scenes.

Total waste of my time. Impossible to use.

not works for some sites. Example - https://www.english-trainer.net/

complicated. Cant add multiple time blocks. Also i want to set block time; not unblock time. UI is complex

It does nothing. Don't bother with this one.

Literally never did what I wanted it to do. I scheduled YouTube to be unblocked 6am to 10pm, and it just blocked all the time! The settings interface was terrible too, it took me forever to figure out how to schedule unblocking at all.