Great extension, an absolute must-have, unfortunately Mozilla has recently decided to be extremely anal about it, so it's no longer supported here. Go to the developers github for newer versions

IMPORTANT: Use old version!
This is a great extension with many useful features. There aren't any alternatives offering the same quality. Amazing work!
HOWEVER, due to some issues explained on the GitHub page, most of the functions are gone in the current version. Until the functionality is restored, you should use the latest "old" version for now, which is 0.2.5. You can find the version archive under the "More information" section of the store page.

It does everything it advertises and blends in so well with youtubes UI. I can't wait till they add more features.

Thank you Particle for being amazing. I've been using Iridium for so long. I hope that my favorite feature, reversing playlists, comes back someday soon.

I don't have a stable income yet, but once I do I'll support Iridium. Thank you so very much for the amazing Add-on.

Works flawless. Although not all features from the older versions are implemented, those which are implemented work flawless, as expected from the author who does an amazing job. I'm looking forward to future development.
Too bad most people give the rewritten version of this addon a negative feedback, but the fact that he now uses a Firefox API to more reliably inject changes to YouTube video player is a very good development. This strengthens this addon and will lead to a much better user experience in the end. Remember when similar addons which claim to disable autoplay actually only pause the video after the page was loaded and if you were unlucky the video was played for first couple of second anyway? (until page loading was finished) This will not happen with this improved injection method. It is really great. I enjoy this so much to never have to worry about any videos starting without my permission. Furthermore this will strengthen Firefox as a browser because this new API is only available in Firefox, not in Chrome.
I'm greatly impressed that the author had the courage to overthrow all legacy code and start a new version of his addon with improved techniques. This is something a lot of developers are afraid to do, and therefore their software dies in complexity.
I cannot understand why people complain because the old addon was broken anyway by recent YouTube changes. So there was nothing to loose.

Going back to previous version... Lets just say that the next time I'll update is "coming soon"

I went back to "Version 0.2.5" and everything works as it should ;)

Im using old version only youtube main page isnt working with blacklist everything seems to work on new youtube. 5 star addon. I didnt like they way you changed version but it wasnt a problem revert to previous version and everything is ok. I'll switch to new version when blacklist works again.

I recommend this add-on 👍