I've been needing something like this for a looong time. Thank you, Sir!

IT BUFFERS AND PREVENTS AUTO PLAY.
BUT I HAVE TO HAVE THE MOUSE OVER THE VIDEO TO SEE IT.
WHEN THE MOUSE IS MOVED ELSEWHERE, THE VIDEO DISPLAYS A THUMBNAIL.

The userscript is very nice. It's a very good idea to stop autoplaying in youtube. The problem is that it does not work properly.

Sometimes a 2nd video frame appears, sometimes the picture "flickers".
So I uninstalled it.

Great script, very handy.

the way youtube should be

My favorite scripts, to make and to use, have one specific functionality, one single target that makes all difference. This is one of those scripts, a small modification that makes a huge difference.

I work at YouTube and I have to do video review for the Partner Program. This task involves opening multiple videos at once in different tabs. I've tried every YouTube Greasemonkey script that exists in an effort to find one that both buffered the video while disabling auto-play. I have been unsuccessful in finding such a script until I ran across this one on Lifehacker and now that I use this one, I could never do my job again without it!

I HIGHLY recommend this script to anyone who watches videos on YouTube!

Does everything I want it to do!