For viewer with YouTube account and high speed Internet connection, and want to always watch all YouTube clips available in higher resolution in high quality mode, YouTube has provided an option in user account setting to set higher quality as default mode of playback when viewing video stream. By default, the playback resolution is set to normal, which means lesser quality.
To change your playback settings to force YouTube to always play video in high quality if available, follow the steps below:
1) Go to YouTube Account page.
2) Under “Account” section, click the Video Playback Quality link.
3) Select the radio button for I have a fast connection. Always play higher-quality video when it’s available option in order to play video in higher quality by default.

Click the Save Settings button to make the change effective immediately.
To revert the selection, choose either Choose my video quality dynamically based on the current connection speed or I have a slow connection. Never play higher-quality video.
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