It's your YoutubeHD add on. This posts details it: https://support.mozilla.org/en-US/questions/1246764 try following this instructions, per jscher2000: An extension named YouTube High Definition has been linked to this problem: https://old.reddit.com/r/firefox/comments/aesm24/youtube_redirecting_to_a_channel/ You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page * "3-bar" menu button (or Tools menu) > Add-ons * type or paste about:addons in the address bar and press Enter/Return In the left column of the Add-ons page, click Extensions. Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Try removing YouTube High Definition, and anything you do not remember installing or why. Any improvement (test YouTube in a new tab)?