The new YouTube feature is especially useful for phone owners equipped with 2K or 4K screens, but used in FHD mode to conserve battery life.
Google has enabled the YouTube 4K / 60p viewing option for most Android devices, even those that do not have higher resolution screens than the FHD. Depending on your phone’s configuration and available processing power, 4K video playback may not work perfectly. And on devices that support 4K video decoding, using this option may involve a slightly faster battery discharge.
Apparently, playing YouTube videos in 4K mode on devices that don’t support this resolution natively has some benefits in terms of overall image clarity and quality. For example, video compression artifacts are much less visible, regardless of the native screen resolution. However, playing video at a level of clarity that exceeds the native screen resolution can also have unwanted effects, in the sense of introducing visual artifacts.
For now, it’s unclear whether the option to play 4K YouTube videos on devices that don’t natively support this resolution is a deliberate change by Google, or an error that will be fixed in the next revision of the YouTube app for Android. What is certain is that Google did not comment on the change observed by the fans. But users who discovered it seem happy and probably wouldn’t like it if Google reversed that decision.