Wonderful Add-On with source code available under MIT License. I replaced "Enhancer for Youtube" with this entirely about a year ago and realized I should probably give it some love. The former is no longer as reliable as it once was unfortunately and this add-on implements most of the same features and just does it better as far as I'm concerned.

A great alternative to the "Enhancer for youtube" that stopped working. The only important thing missing at this time is the popup player that appears as you scroll down to read the comments. Thank you for making this.

Great little add-on for Firefox. Still giving it 5 stars despite the playlist annoyance.

There's no setting to disable the add-on from hiding playlists which means no auto-play music. I can disable the add-on, but I still have to restart Firefox to see playlists again.

Edit: Disabling the add-on actually does nothing even with restarting. I wish a setting to view playlists was a thing.

I like your extension thank you, so I have some requests; can you add "Pop-up player" when you scroll down for reading comments need to continue to watch the video..
and can you add "Automatically expand the video player" not just a manual button.
the last one is "Automatically sort comments from newest to oldest" this improvments will be perfect for the extension. Best Regards.

Answer to Developer: Thanks for your response.
"Are you talking about maximizing the player?" Yes automatically maximizing. Waiting for new features.. Thanks again. I wish you success.

By far the must-have youtube extension for me. Thanks!

is the best EXT in FireFox And Othe Browsers,,TNX

Serious developer

Takes your youtube to the next level.

i had read about you and everything seems promising, i hope you continue being this proactive in the future!
I'll change the review with my experience using the extension, could take a while since the experience can be too good and make me forget!

Edit: after quite some time i had no bugs at all and i'm liking it pretty much! the playback speed buttons could work more like the competition one though, thank you!!

Very good add-on. It's early in development, but works generally well, it's aesthetically pleasing, and the author is actively improving it and fixing bugs -- I'm glad the bug I reported on the volume boost was fixed so quickly. Can't ask for more. Btw, current version 1.24.1 seems to not be able to copy JPEG images to clipboard -- file saving works fine!

Good work. Cheers.

La verdad que es una cagada la extensión y deja mucho que desear, flojito flojito, la otra extensión era mejor que esta, no se por que la sacaron?

PD: Lamento mucho mi comentario desafortunado y mal educado, estaba enojado y de mal humor la verdad no era mi intención de ser tan desagradable, estaba enojado por que quitaron la otra extensión y descargue todo mi odio y frustraciones hacia vos y tu extensión, y te pido disculpas por eso.

Love it :)

This is a good extension and it does what I need it to with a minimum of fuss. It would be improved if the Maximize Player button wasn't hidden behind an options menu you need to hover over, though, or even possible to set up as automatic. It's basically why I'm even using this extension at all and making it easier and faster to turn on and off would be much more convenient.

edit: I am enjoying the new improvements to this. I wrote a new review, because I don't know if you'll be notified of changes to the old review, but it has been much better since the update. I would recommend renaming "video history" to something more informative, though. It took me a while to figure out where this annoying "continue video?" pop-under and shader were coming from. It is not what I thought it would do. Otherwise this is very good work.

Pretty decent replacement for the Enhancer for Youtube extension that went down. I mainly only used that extension for its automatic theater mode and automatic quality adjustment feature, and this extension has those features as well so it works as a replacement in my case, at least until the original enhancer extension comes back, if it ever does. Thanks a lot to the developer for providing this extension.