This bookmarklet allows you to "redirect" from videos that got private or deleted (or still alive) and was preserved by tubeup.
The reason this script exists is because videos archived with that program will become hidden to everyone except the archiver, meaning no one can find the videos. However, you can still access them by using the same URL with the video id, which is what this script does (although not automatically).
It does this by opening a prompt where you can paste the youtube URL you want to find. In the no copy version it still opens in a prompt, but the URL on the current tab is used.