Does exactly what you'd want (unlike a couple of alternatives I tried.) Takes a few minutes to set it up how you want it, but is flexible enough to either block specific sites, or block everything except for listed exceptions. It can block them through your workday, or after you've been on them for X minutes/hours, or a combination of the two. You can hit a button to override the block, or you can configure it so that overriding requires a password, or is not possible at all!

For those who use profiles: I use one Firefox profile for work, and one for personal stuff. I installed LeechBlock on the personal one, to block everything during my workday. This seems to work well for me.

Thats reallme cool. Thanks for developing this, you are the only one with such a big functionality.

Very helpful productivity tool

Love it!

Perfect!

great usage, crisp UI

Great tool, helps with focus and avoid distractions

I am trying to not waste my time on derogatory things, this helps.

genuinely excellent -- customizable, stable, helpful

Does exactly what it says on the tin. Feature-rich as well.

While working WFH, this tool is life saver. I was not able to control myself watching YT videos, scrolling facebook and instagram and this tool changed everything.
Thank you so much to developers!

Best productivity add-on with a LOT of features. I find the programmed blocking very useful as it helps prevent the triggers of distractions. Unlike Forest for example where you have to pay for additional features and where you have to manually configure each session.

The best of his kind

Insanely useful app that has helped me stop wasting time on social media and has gotten me to do more fulfilling things with my life! Great options and customization with their block system so that you can pick and choose what is allowed.

Nice

This extension has done a huge job in helping me to concentrate studying at home. Being at home, I can easily get lost while navigating online losing the focus on studying. This app allows me to see that I need to focus, such that I can be productive during the day!