Works 99% of the time and is super useful to me. The one caveat is when you visit a youtube homepage. The default video sometimes will play regardless of how this add-on is set. Other than that quirk, which is somewhat of a corner case, this thing is excellent.

Working on OSX FF 81.0.

Will bump up to 5 stars after soaking for a few days, to make sure it plays well with others (plugins that is)

As the previous reviewer pointed out — no "Up Next" boxes. It returns to the start of the video, paused, with the play button in the middle so you can play it again if you wanted. That's OK. There's still the recommended videos down the sidebar that showed much the same selection anyway.

Work like a charm!

It would be nice to still be able to turn it back on when I feel to.

Works when clicking on a link directly but doesn't when opening a youtube video in a new tab. What's odd is it used to. I recently had to reinstall windows. Somethings changed, I don't know where... possibly at youtube because this addon used to work on videos opened in new tab. Note: None of the 'stop auto play addons' (if that's what they are?) work on videos opened in a new tab anymore so possibly youtubes changed something.

It's not work anymore since YouTube updated new UI in my country.

0.1.2.1 no longer does the job, and 0.1.5.1 is not available for Firefox ESR 45. Looks like the eternal hunt for working addons that fix crap on the internet just started again.