magnets affect on a phone

Magnetic fields can temporarily interfere with the digital compass and magnetometer inside your smartphone, and that’s more serious than you may think.

The problem we found is that a nearby magnet will affect the internal magnetic sensors inside the phone. The compass won’t read correctly,”

You might think it’s unimportant because you never use the compass app, but that doesn’t mean other apps aren’t relying on the same sensor. Google Maps, for example, uses the sensor to detect which way the phone is facing, and a number of games also rely on it to work out your orientation.

This is something that Apple considers in case and accessory design. In Apple’s Case Design Guidelines, there are sections on Sensor Considerations and Magnetic Interference, including the line, “Apple recommends avoiding the use of magnets and metal components in cases.”

Manufacturers have to ensure that the built-in magnetic compass is not affected by their cases. There’s also specific mention of the iPhone 6 Plus, because of potential problems magnets can cause for the autofocus rear camera with optical image stabilization.

Magnetic accessories might interfere with iPhone cameras - Apple Support