I do it via `document.getElementsByTagName("video")[0].playbackRate = 3.0` in the dev console. You can up arrow to it similar to a normal terminal on the next video. The nice thing about this is you can put any float in e.g. 3.333.

There are also extensions of course.

You can also put this:

  javascript:(function(){document.querySelector('video').playbackRate=3.0;})();

as a bookmark on your bookmarks bar.

The extension he probably used is Video Speed Controller; it works on any HTML5 video, and you're not limited by whatever UI they've wrapped around that built-in functionality.

Streaming and download/playback tools can offer greater flexibility. I typically use mpv, though other options are mps-youtube, or for download + playback, youtube-dl and xine, mplayer, mpv, mps, or VLC.

I find I can typically listen at 1.25 - 1.75 readily. Exceptionally poor content I'll bump to 2x. I don't generally go much above that unless I'm fast-forward scanning video for specific content.

I created a simple browser extension for this purpose, "YouTube Turbo Button". As mentioned in the other comment, it can be easily done through the console, but I found having a button for it more convenient.

Opening directly in `mpv` gives a wide range of speed control, has keyboard shortcuts for everything, and as an added bonus, skips ads by default.