iOS: PokéStop Scanning is available on iPhone 6s and newer devices running iOS 11+.
Android: PokéStop Scanning is available on devices running Android 7.0+ and can support Google Play Services for AR. Supported devices must install Google Play Services for AR from the Google Play Store. A list of supported devices can be found here.
Note: PokéStop Scanning/AR Mapping is different from AR+ mode and Reality Blending and has different device requirements.