When watching a video on YouTube, the player only buffers a short time ahead, even when the video is paused. There used to be a time when videos were buffered to the end, which allowed a smooth watching even on slow connection. But at some point YT's streaming algorithm was changed, w/o an option in the setting.
Over the years there's been a couple of workarounds (as plugins or extensions like SmartVideo for YouTube), and there are a few older discussions in SE and other places. However, those do not seem to work anymore.
Is there a way to buffer a YouTube video, for smooth watch over slow connection?