Probably if you have a fast internet connection and no download limit for your internet connection, you would always to watch the videos in High Definition (HD). By default, the YouTube videos are streamed in normal quality. If you want to watch it in HD, you will have to specify it. This is how you force YouTube to play videos in HD.
- Click on YouTube settings
- On the left side, Click on Playback
- Under Video Playback Quality, Select Always choose the best quality for my connection and player size and Select Always play HD on fullscreen.
If you have a slow sluggish internet connection, it is better to select I have a slow connection. Never play higher-quality video.