Those who watch YouTube videos on smartphones may have noticed that it is not possible to play any video in the YouTube app at a resolution of maximum 1080p and 1440p. Until now, it was not possible to play 4K videos on YouTube's mobile app, as YouTube 4K playback support was turned off on all devices except native 4K screen resolution devices. And, at present, there are very few smartphones in the market with a native screen resolution of more than 1440p. So it was not possible to watch videos in 4K resolution in the YouTube app on any other smartphone except a handful of smartphones.
Although many third-party YouTube apps, such as NewPipe or the YouTube Vanced app, can play videos in 4K resolution, they have never been a permanent solution. However, this time YouTube has added native 4K playback support in the latest update of their smartphone app. In other words, from now on, if you want, you can play videos at 1440p and 4K resolution directly on the official YouTube app on 1080p screen resolution devices, if your internet speed is enough to play 4K videos. However, if your device's hardware is not powerful enough to play 4K videos, then you will not be able to enjoy smooth video playback.
In order to get the 4K quality option in the settings, the video you are watching must also be uploaded in 4K resolution. If you haven't yet got the 4K resolution option in the YouTube app, then update your YouTube app from the App Store or Play Store. And if the latest update of the YouTube app is not yet available to you in the Play Store, you can manually download the latest version of the YouTube app from the Apmirror website!