YouTube has long allowed users to stream high-resolution videos on the desktop regardless of whether their display supports those resolutions. For example, users on Full HD displays have been able to stream 4K videos or higher as the service downscales the video to be run on lower resolutions. However, the case on the mobile app has been different, since it restricts resolutions higher than that of the display.
That is changing now, as users have begun reporting on Reddit (spotted by XDA-Developers) that the Android app is offering the option to stream videos at up to 4K resolution at 60fps on some devices, regardless of whether the device’s display resolution is that high. In our testing, the option to stream 4K videos on mobile is present on some devices, mostly those with a resolution of 1080p or higher. However, not all devices with Full HD displays seem to offer the option. The Moto G5S Plus limits the resolution to 1440p. On the other hand, some 720p display-sporting phones like the Redmi 3S Prime offer up to 1080p resolution.
While the change makes it possible to stream higher fidelity, sharper videos on mobile devices thanks to the downscaling of content, the difference in quality on a small smartphone screen might not be as visually significant as on a larger display. Additionally, the higher bandwidth requirements for streaming larger resolution videos might cause a strain on those with lower internet caps.