Title says it all. I used to use an extensions called smart video for youtube, but apparently that is now dead along with youtube center.
I have 150mb/s download and I can stream 4K on netflix and some other websites without any real issue, but youtube's stupid caching thing has made it difficult to watch 4K without a crap ton of stuttering.
Do you have things downloading in the background, like steam? because for me every time an update or I'm downloading a game, everything slows down not just for me, everyone whose on the internet
Youtube removed the old pause & buffer the whole video feature. Now it might be on a setting somewhere but its bound to be awkward and flaky. Just another YT regression.
When they first introduced html5 video on youtube (youtube.com/html5), the player would do exactly as what you're looking for. The downside is that it had very limited features like only 720p max resolution etc. When they updated it to be in line with the flash variant (eww), that feature was removed. Using something like youtube-dl might get what you want.