A simple auto-HD script, which does not re-format the page as YouTube Center does. Very fast.
Sets the resolution of all videos on YouTube to the resolution set in the script.
Disables DASH playback
Disables autoplay on video pages.
Pauses videos on channel/user pages.
Pauses videos if a video is started on an inactive tab.
Converts links in comments to open in a new tab
Disables switching to the sharing tab at the end of a video
All of these features can be disabled with some console commands. Go to a YouTube page, open the console, and settings are stored in an HDOSettings object. It has properties:
HighestQuality (number from 1 to 9)
Change these as you like, and run SaveHDOSettings() in the console to save your settings. See screenshot for help. For example, this code will set the desired quality, enable autoplay and save changes: