youtube
Is there a way to always watch YouTube videos in HD (when available) and without changing the resolution yourself?
YouTube offers 360 standard for small player, 480 for large and 720 for full screen.
I would like to have the 720 video high definition version. Always.
Seems that the best YouTube supports is specifying that you want HD (720p) if available. That's accomplished by appending &hd=1 to the URL.
Almost a year ago, someone asked pretty much the same question on the YouTube support forum and got "Thanks for bringing this to our attention; we are looking at how to resolve this, and I will update you accordingly." from a Google employee, but I can't find any evidence that a fix has been released since then.
Some videos on YouTube are uploaded in a high resolution, for example 720p (720 pixels vertical resolution). However, the player window itself is just around 380 pixels high.
When you watch the video in the small player, it doesn't make sense to buffer the high-quality version. You wouldn't see all the pixels anyway.
When you switch to full-screen, notice that the resolution indicator in the bottom right can change, for example, to 480p or 720p, which is a completely different stream. Therefore, it has to be re-buffered.
You can change this behavior under Settings » Playback Setup » Video Playback Quality:
Best Answer
I don't believe that there is a setting in YouTube to do this. You can achieve this by installing this GreaseMonkey script though.