The YouTube app defaults to 480p the first time a video is opened. It is assumed that switches to your screen resolution a few seconds later. However, this is not always the case. The regular YouTube app does not let you change this behavior, but like most things with Android, there is still a way.
There is a modified version of YouTube known as YouTube Vanced that contains a number of features that do not exist in the Play Store version. One of these features involves changing the default video quality for mobile data and Wi-Fi. This eliminates the need to wait for the app. While there is a method for rooted users, the process we will discuss below does not require root.
: Download YouTube Vanced
YouTube Vanced needs to load sideways. Therefore, ensure "Unknown Sources". or the "Install Unknown Apps" permission is enabled on your phone. If you'd like to sign in to the app using your regular YouTube account to view your subscriptions and history, you'll also need to download an add-on called MicroG. MicroG is an open source replacement for Google Play Services, and while this may sound complicated, installation is as easy as loading any other app.
To start, tap the link at the bottom of your phone and select "MicroG Vanced." msgstr "To download the add – on, press" Install "when prompted, then go back to the same page and select the first entry in the list to download YouTube Vanced. Install "when prompted.
After installing the app, two YouTube apps will appear on the phone, the default YouTube app and YouTube Vanced. You can simply hide the second app with a custom launcher such as Nova
Be forewarned that the APK file may contain malware as you load this app sideways, unlike the Play Store, where Google's apps are scanned, you trust the modders for what they promise very popular app with a large community of users, so you should be fine, but please download it at your own risk.
Step 2: Change the default playback quality  Now open YouTube Vanced and in the top right corner select your profile picture (or the silhouette icon) and then select "Settings". Select "Vanced Settings" and then "Video Settings".
Select "Mobile Preferred Video Quality" and choose the screen resolution you want for videos you watch while connected to mobile data. Then select "Preferred video quality for Wi-Fi" if you want to change the default resolution for a Wi-Fi connection, and then select a resolution.
Besides the standard resolution for playback, you can also use your device View videos at a higher resolution than your screen. With this additional resolution, the video is reduced to the resolution of your screen, resulting in a sharper picture thanks to the added data. Note, however, that more data is consumed at a higher resolution. If you do not have an unlimited data plan, by default you only use the higher image (eg 2160p or 4K) for a Wi-Fi connection.
tap the Back button until you return to the main page, and open a video. As long as the creator of the video has uploaded the video at the desired resolution (or higher), it should start with this resolution instead of 480p. If you have a different resolution for Wi-Fi, join a Wi-Fi network and watch another video. Again the resolution should be chosen as default.