Google this evening released a minor update to the YouTube for Android app, bumping it to version 5.7. The update doesn’t add much, but does finally add one long awaited feature. With YouTube 5.7, you can now manually choose the quality in which you want a video to playback.
In previous versions of the app, you could only toggle between HD and HQ. Now, you can choose from 144p, 240p, 360p, and 720p. 1080p support appears to still be missing. The auto option will presumably choose the best stream based on your internet connection at the time of playback. To bring up the quality toggle, click the action button on the upper right corner of a video, then click the settings gear icon.
The update is rolling out slowly to Android devices, so it may take a little while to hit your device. In the mean time, keep an eye on the Play Store.