Greasy Fork is available in English.
Quickens the bufferer on all Youtube videos
First off, this script was initially made to benefit individuals in the US, although it also surprisingly works well here in Australia, and I am sure most other locations around the globe would benefit.
This script simply changes the server location that is sending you the video data from your local, potentially crowded server, to one in Canada that amazingly, on average, has a lot fewer clients requesting data. The benefit of this is the Canadian servers have the highest chance to have cached a recent upload that is popular in the US, but without the traffic of the US trying to download this cached info.