Find My is Apple's location tracking and anti-theft network that securely links a device's hardware identity (IMEI and serial number) to an owner's Apple ID. Enabling this feature automatically engages the Activation Lock on Apple's servers.
When purchasing a used iPhone, a buyer must ensure the previous owner manually toggles off the "Find My" feature in the settings. The system will require the original Apple ID password to authenticate the request, severing the cryptographic link between the hardware and the account and allowing safe resale.
