Using the provided controls, YouTube video speeds can only be adjusted from 0.25x to 2.00x. A speed outside of that range is sometimes desirable.
I generally prefer to listen to videos at 2.75x. It depends on the video, however, 2.00x or 2.50x is often a little too slow and 3.00x is generally a little to fast. Your mileage may vary.
Create a new bookmark and name it something like 2.75x. Change the address to the following code for a 2.75x YouTube video speed bookmarklet.
Different bookmarklets can be made for different fixed speeds. Just create another bookmark with the correct name, add the above code, and change the value of the playbackRate variable in that code to the correct value. I have a YouTube folder on my bookmark bar that contains a list of bookmarklets with different playback speeds.
1.00x (to reset the video speed)
2.00x (useful in a bookmarklet list)
4.00x (generally too fast)
Alternatively, the following code can be used to prompt for the desired playback speed. Note that video playback may stop while the prompt is active, depending on the browser being used.
The bookmarklets can additionally be used to speed up ads. This is not possible with the provided controls. Either use the above bookmarklets to efficiently absorb advertising material, or use something like a speed of 100.00x for rapid playback without audio.