Whether you're curious about a device you purchased or want to see how well a phone runs before you sell it, here are the best diagnostic tools for iOS and Android.

Designed for both iOS and Android, TestM can run diagnostic tests to check your screen, sound, camera, connectivity, and other features.

If you repair your ‌iPhone‌ using ‌Self Service Repair‌, you might be asked to put your ‌iPhone‌ in diagnostics mode as part of the System Configuration process.

TestM for iPhone and Android Designed for iOS and Android, the free TestM app can run diagnostics on your phone's touch screen, sound, camera, sensors, network connectivity, and other hardware.