This is a much needed and appropriate port from the best Chrome extension for video controlling. Works great, unfortunately it doesn't seem real that it would work starting from Firefox 48 as described. As I'm using Waterfox (FX 52 ESR equivalent), v0.5.1 is the only one really doing the job (attachShadow problems).

doesn't seem to work for amazon prime video, at least not correctly (doesnt visually show speed change in the extension UI), the speed might change only sometimes when the buttons pressed on amazon prime vid. only site I have issue with

Works very very well, but stops working whenever I use an equalizer addon to filter out some background noises.

best one out there, but needs and update!

Works really well, only issue I have is even when I blacklisted the extension from working on Twitch, it still randomly makes streams play in 1.03 speed which causes the audio to artifact hard.

Needs per-domain persistence, not global

You can control with shortcuts, but buttons such as + and-are not displayed.
Do I need to do anything?

it's great and super helpful! but could you add a reset button? i sometimes speed up during advertisements and then i have to click multiple times to get it back to 1x

edit: ok, pressing "r" resets..... i just usually use the actual controls, and there was no button for it. you might want to consider adding it!

The controls not always show up on the video. How to make the controls to show up?

A absolutely must have extension. Unfortunately it is not updated and cause malfunction on some pages like this one
https://www.ellinikahoaxes.gr/
(thumbnails of videos do not load)
IMO that should be a build in firefox feature not an extension.
That alone, that this extension is no longer updated, is reason enough for me to consider switching to chrome.

Works great, does exactly what I wanted it to, except for one thing:

When the add-on is enabled, I can't play two videos at the same time (say, I have two YouTube tabs open for, say, a podcast with no background music and background music). I don't know why; I don't know if that's a bug or a feature, but if it's a feature, it's a bad one, and I'd at least like to see an option to disable that.

If it is a bug, please fix it. I'm adding it as an issue on your GitHub.

Keep up the good work, though. Again, I gave this a 4/5 for a reason.