1) search for channel name on youtube search.
2) right-click on the name of the channel to block
3) block videos from this channel
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Thank you firefox_is_open_source for your comment. I was going to to give up on this add on till i saw your comment.
After all that hard work developer getting bad review because he forget mention it clearly how this work. May be its some thing obivious for user who used this addon previously but no for first time users like me.
Any way thank you Dev for your hadwork. Keep up the good work.
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About addon- Works like a charm. You can filter useless you tube garbage through this nicely. After blocking channels, better to add channel name as a keyword for popular channels.