This extension does block YouTube from recommending channels but it is NOT user friendly. The input box is displayed below a list of all blocked channels so one has to scroll endlessly to get to. Fix: Put the input field at the TOP of the page. Additionally, the list of blocked channels is not alphabetized so if you ever want to remove a channel, you have to look at EVERY blocked channel. Fix: Alphabetize the blocked channel list.

I would give this extension a 5 star review if the aforementioned issues were fixed.

DO NOT USE. Installing this addon broke Firefox for me; I couldn't use my Back button, nor could I type into the address bar. Issues persisted after the addon was removed, so something seriously dodgy is going on.