So, the default size of the video player on YouTube is quite small. I know, right?

Expanded view is much better. Tell me about it!

But why doesn’t the damn website remember you switching to expanded view yesterday? Because it just doesn’t offer the functionality.

I am about to change that and rock your world.

The solution: User CSS

Just create a file called youtube.com.css, or something like that, and put this code in it:

div#watch-player.flash-player,
div#watch-video {
	width: /*854px*/ /*970px*/ 1280px !important;
	height: /*510px*/ /*580px*/ 765px !important;
}
div#watch-sidebar {
	margin-top: 10px !important;
}
div#watch-video-container {
	background-color: #555 !important;
}

To elaborate on those values:

854 x 510 pixels is the default size of YouTube’s Expanded View
970 x 580 pixels is the full width of the YouTube website
1280 x 765 pixels is true 720p size and will load videos at 720p by default, because of the player’s size, ZOMG!

You can (un)comment any set of values you like, or choose your own. Be sure not to make it bigger than your screen is capable of showing, because that would be a waste.

As for putting this file to use on the YouTube website, I refer to the internet.

Some visual examples

(because people’s attention span isn’t getting any better any time soon, they may even have stopped reading after the first sentence – not because I’m a bad writer, oh no):

The video player at default size

The video player set to Expanded View

The video player at full website width

The video player at full 720p width