iOS 15 brings some really nice features to popular apps like Facetime and Photos, but it also brings another cool feature called per-app accessibility that lets you change text size, transparency, button shapes, labels, and more for every app installed on your device. You can customize individual apps to your liking and get the most out of your workflow with this feature. Here's how to use per-app accessibility on iOS 15.
Per-App Setting in iOS 15 I iOS 15 Hidden Feature to Customize Individual Apps on iPhone
Open the Settings app and tap 'Accessibility'.
Now scroll down and tap on 'Settings per app'.
Tap 'Add App'.