Youtube application on Android allows you to play videos up to 4K resolution. All you need is a 4K screen phone and a decent internet connection and you are OK. However, it seems that Google has now opened up unsupported video resolution options on some devices, allowing some users to play 4K videos on a low-resolution device.
According to some recent posts on the YouTube subreddit, the YouTube app on Android now lets you play 4K videos even if you do not have a supported device. As shown in the following screenshot by the Reddit u / Liskowskyy user, the application now displays all video resolution options up to 2160p60 regardless of screen resolution.
While some believe that this change is unintentional, one user in the comments on another Reddit user u / sssxun suggests that the change may not actually be error. They claim that by allowing unsupported video resolution options on devices with lower resolution screens, videos will have higher fidelity than reproduction in supported resolution. We tried it in one device with 1080p screen and the videos seem to look much better than when played at 2160p60.
As another commenter points out, the dramatic improvement in video quality is due to the fact that higher resolution videos have a higher bit rate and therefore less "blocky compression artifacts" on high motion screens. Playing higher resolution video on a low resolution screen also increases sharpness due to the scale reduction, making the video look better overall.
Unsupported video resolution options appear to be widely available in various versions of YouTube in Android. We tested some devices and were able to find additional resolution options on all of them, even though they were running different versions of the application. This leads us to believe that he can have activated via a switch on its side server.
Source of information: xda-developers.com