Greasy Fork is available in English.
Periodically records the current playing time while you watch videos, so you don't lose track of where you were watching.
Userscript by agj. Works on Youtube.
It will periodically save the current position of the video you're watching, so that if the page gets reloaded you won't lose your position. The way the position is saved is on the URL itself (the t=1234 part of it).
t=1234
License: Unlicense