Google (YouTube) announced last week, that starting this week, YouTube will begin displaying videos in full 1080p HD. Up to this point, YouTube only offered 720p HD video. YouTube will encode new video uploads at their full resolution and will re-encode previous uploads to their full resolution too (assuming the videos are/were uploaded at 1080).
The 1080 and 720 refer to the horizontal lines of resolution in a video…1080 means more horizontal lines in a video, which means sharper quality.
That also means that now you can watch someone’s shaky video of a birthday party in all it’s intended glory.
But only about 10% of video uploads to YouTube are HD, so other than featuring some of the best HD videos on their homepage, don’t expect any other sweeping changes on the site.
Also keep in mind that 1080p video, on the web, is going to be very resource-intensive on the viewer’s computer during playback. Which means that currently, many people won’t be able to watch them without experiencing some sort of playback issue.