A good add-on, but no longer maintained. Youtube redirects don't respect browser autoplay settings, and play on load - annoying!

This add-on was forked and continues to be maintained as LibRedirect: https://addons.mozilla.org/en-US/firefox/addon/libredirect/

Great addon but discontinued, checkout the fork libredirect:
https://github.com/SimonBrazell/privacy-redirect/issues/408