Firefox — Youtube Center

YouTube Center let you disable DASH playback. Why does that matter? With DASH off, the entire video would buffer, not just the next 2 minutes. Perfect for slow or unreliable internet connections.

While you cannot (and should not) install the original today, its DNA is everywhere. Every time you use a modern YouTube tweak, you are standing on the shoulders of YouTube Center. youtube center firefox

You could set auto-play to be off by default—a feature YouTube didn't officially offer for years. YouTube Center let you disable DASH playback

You could force YouTube to buffer the entire video instantly or adjust how aggressively it pre-loaded data. the entire video would buffer