Excellent, simple to use, highly flexible so that you can setup the kind of help you need. It really helped me improve my focus at work.

Works almost as intended. I blocked Youtube for starters and as long as I'm actively interacting with or giving focus to firefox, the counter is ticking down. The moment I'll click on something on my second monitor (in this case, Discord) the counter stops after two seconds. This has been reproduceable. I'll use it further as a reminder for myself, but sadly it's not working as I need it right now :/

Edit: Thanks! Is working as wished :)

I can't thank you enough. I have installed old version of firefox just to use leechbock.

This ad-on saves my life! it is highly customizable, and can surely support your needs. I love you LeechBlock devs :)))))

Just when you thought there was no paradox in leech blocking to be found, Prof. James Anderson displays a thorough "analysis of its character, presence, and epistemic status" for the interwebs! Well done...

It works almost perfectly. I hate it. Uuuuuugh, guess I'll go back to work. Anyway, it's 4 instead of 5, because the temporary unblocking feature doesn't seem to work. The icon is yellow and everything, but the websites aren't unblocked.
Edit: see developer response, it was user error.

Bescherm je zelf tegen afleidende websites zoals zogenaamde "sociale media" en nieuwsmedia.

Set a timeout and block sites for a duration, then refresh the time limit. Plus tons of customization for every combination of limit - limit during a set time of day, or set limits /except/ during a set time of day. There are even thoughtful and creative options for making websites unpleasant to use to wean off of bad habits without going fully blocked. Everything I could ask for plus gave me some new ideas for how to manage my time and break my bad habits. I'm fully impressed.