Description:

This script ensures that all YouTube videos (including Shorts) play at the user's preferred quality setting. It supplements YouTube by addressing the issue where the browser version does not allow users to save their quality preference. The script monitors whether the video quality can be adjusted and uses the YouTube API to apply the chosen setting. No bloat, doesn't do anything else, just sets quality.

Features:

• Lets you save a preferred video quality.
• Sets the video quality to your choice.
• Uses a UI menu for easy quality selection. [New]
• Applies Premium bitrate when available. [Requires YouTube Premium]
• Adds an 'Optimized Auto' mode. [New]

Notes:

• If your chosen quality is unavailable, the next best available option will be used.
• Changing settings cannot be done on embedded sites. Go to the YouTube website when you want to change your quality preferences.
• The quality preference applied by the script can be temporarily overridden through the native YouTube UI.
• Tampermonkey only added dynamic menu items in version 5.4.6224, which is still in beta as of writing this. This script would fallback older Tampermonkey versions to a static menu to maintain compatibility.

Compatibility Status:

• COMPATIBLE with YouTube in all languages.
• COMPATIBLE with YouTube videos that are embedded in other sites.
• COMPATIBLE with most desktop browsers, but the ability to change settings relies on the script loader having the ability to display custom menu items.
• COMPATIBLE with the mobile website (m.youtube.com) but may work less optimally.
• LIMITED with AdGuard for Desktop. The script functions properly, but the setting UI is completely unavailable, so settings must be adjusted directly via script storage (reported by SeriousHoax in the script discussion).
• INCOMPATIBLE with iOS and iPadOS.

Extra comments from me:

Summary:
This script is modified from YouTube HD by adisib. Since adisib's script is severely outdated, this script was created to fix broken functionality and improve user experience. At this point, this script is completely different from adisib's, with new features and a separate objective.

What has been changed:
The way the Premium bitrate option was written by adisib contained a bug that made the script treat the Premium option as unconditionally unavailable. It would also fail to apply premium bitrate if YouTube was set to anything other than English. Fixing those issues was a major goal of this script. All broken or outdated features have been fixed or removed.

The goal of this script is to override YouTube's quality negotiation. However, since the creation of this script, YouTube has improved its auto quality to the point where I would start to consider it usable. Thus, an 'Optimized Auto' option has been added to ensure that YouTube always selects the Premium bitrate when appropriate.

What's new:
A UI menu has been added for user preference management. Adisib required users to edit the script directly when choosing their quality preference, which was very unintuitive and caused frequent false bug reports. My implementation should hopefully be more convenient, and be compatible with most users' browser + script-manager combinations.

(Updated Feb/21/2025)