Here's how to link directly to full-screen and HD versions of your video. We're not sure when it was disabled, but the old &fmt= suffix doesn't work any more for determining resolution on YouTube.

YouTube will default to SD resolution whenever you play a video. For faster Internet connections, select "Always play HD on fullscreen (when available)" and click "Save." ...

Universal Music Group and YouTube have teamed up to remaster iconic music videos from standard definition to HD. The partnership will result in more than 100 music videos from artists like Janet ...

When playing previously-purchased HD media from Google Play Movies, the YouTube player is limiting playback to 480p. No other options for higher resolution playback are available — such as 720p ...