Greasy Fork is available in English.
Tells YouTube that your browser only supports videos at 30FPS or less, which switches all 60FPS videos to 30FPS and allows old computers to watch high-resolution videos without stutter!
< Feedback op Disable YouTube 60 FPS (Force 30 FPS)
Script broke at 9th August 2020. 60fps shows up on 720p instead of plain 30fps. RIP