How iOS 15 Tracks Location When Powered Off

With the release of iOS 15, Apple upgraded its Find My network to locate iPhones even when they are powered down or depleted of battery. This article explains the underlying hardware and software mechanisms that enable this capability, including the Always-on Processor, Bluetooth Low Energy beacons, the crowdsourced Find My mesh network, and the end-to-end encryption protocols that keep user location data private.

The Low Power Reserve State

When an iPhone running iOS 15 is turned off manually or shuts down due to a drained battery, it does not completely cut power to every internal component. Instead, the device enters a specialized low-power state. A small reserve of battery is retained specifically to power critical background subsystems, allowing certain chips to function for up to 24 hours after the device is powered off, or up to several hours after a battery-depleted shutdown.

Always-on Processor and Bluetooth Beaconing

During this low-power state, the main application processor (the primary CPU) and the display remain off, but the device's Always-on Processor (AOP) and the Bluetooth controller stay active. The Secure Enclave continues to generate rotating cryptographic keys, transforming the powered-down iPhone into an active Bluetooth beacon, similar to how an Apple AirTag functions. The phone continuously broadcasts short, low-energy Bluetooth signals carrying these encrypted identifiers.

The Crowdsourced Find My Network

The broadcasted Bluetooth signals rely on the broader Apple ecosystem to relay their position:

  1. Detection: Any nearby Apple device (such as an iPhone, iPad, or Mac owned by another person) that comes within Bluetooth range detects the beacon signal.
  2. Relay: The detecting device captures the beacon's public key, notes its own current GPS location, and securely bundles this data.
  3. Upload: The detecting device then transmits the bundled packet over Wi-Fi or cellular data to Apple’s servers. The owner of the helper device is completely unaware of this process, and it consumes minimal system resources and data.

Privacy and End-to-End Encryption

The tracking process is protected by end-to-end encryption to prevent tracking by third parties or Apple itself. The public keys broadcast by the powered-down iPhone change frequently to prevent physical tracking. When a nearby device uploads the location payload to Apple, the data is encrypted using the target iPhone's public key. Only the rightful owner, logged in with their Apple ID on another trusted Apple device, possesses the corresponding private key required to decrypt the location on the Find My map.

Hardware Requirements and User Control

This feature is supported on iPhone 11 models and newer running iOS 15 or later, as older models lack the hardware architecture required to keep the Bluetooth controller active while the primary system is shut down.

Users retain control over this feature. When sliding the power slider to shut down the device, iOS displays a label stating "iPhone Findable After Power Off." Tapping this message gives the user the option to temporarily disable Find My tracking for that specific shutdown cycle, fully powering down the Bluetooth radio until the device is manually turned back on.