Unbelievable. The author has dissected YouTube.

The number of features is staggering. There is something for everyone—too much to list in this comment; you have to try it yourself.
Amazingly, every option is explained via tooltips, so you know what to expect. The UI has a clean and elegant style, something that browser addons often fail to achieve. After finalizing your settings, you can export them and easily apply them to any device and browser.

I was using YouTube Enhancer before, which had a fraction of the settings that this extension offers, and some of them didn't even work!
Frankly, the former looks like a joke when put next to this one.

These should be the official YouTube settings, and the author should be employed by Google, collecting big paychecks. This addon simply feels like a part of YouTube.