Very helpful add-on. It has only 1 bug that is It reset playback speed to 1X when page get refreshed or new video is selected to watch on the same Tab. Please fix it.
Overall BEST add-on.

simple and reliable

Good for increasing the speed of YouTube videos beyond YouTube's own limit of 2x.

Partly works on YouTube in Firefox Nightly for Android. Controller indicator works in desktop view. In mobile view, it doesn't respond to touch, disappears after a couple of seconds, and can't be brought back with a tap. Switching to desktop view is a reasonable workaround, but fix the mobile-view issues and you'll have a complete winner.

YouTube High Definition has to be disabled for the "force last speed" function to work. No worries about that, but just an observation for anyone puzzled by the function not working.

Would be great with these improvements

* Have a whitelist, which is opposite to the blacklist we got now - so only websites that we pick this extension will work on.
* Have on option that shortcut keys will only work if the video is on full screen.

Great! Works well on most videos. Super useful and easy to control with keyboard keys. Thanks.
Sometimes switches between the little box top left and a larger box with text in it, but flicking faster and slower (s/d) can get it as-wanted.
The little speed box normally top left can appear in the middle of the video - not so helpful but can be dismissed with the X.

Works great on most sites, not working with Netflix though, please try to add support for netflix on firefox?

helps remove blurring of videos in HTML5 by increasing speed to 2x, 3x or 4x as it blows away blurring by pushing speed

add a shortcut to go back to the beginning of video 。

This extension has not been updated for 7 months. I updated it for myself on the github.com/0x7633/videospeed-firefox#install-chrome-or-firefox-extension.

大部分情况都是可以的,小部分情况下可以进入设置进行调整.但是当看合集视频的时候(比如Bilibili动漫合集),单击进入下一集的时候,这个插件就不能工作了(但是保留了之前的播放速度,因为设置中开启了记住倍数)

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!