Since a force restart has already been tried and the boot loop persists on your friend's iPhone 13, the next step is to use Recovery Mode to repair the iOS system. Here is how:
1. Enter Recovery Mode on iPhone 13:
- Connect the iPhone 13 to a Mac or PC using a USB-C to Lightning cable
- On Mac (macOS Catalina or later): open Finder. On PC: open iTunes
- Then quickly press and release Volume Up
- Quickly press and release Volume Down
- Press and hold the Side button
- Keep holding even when the Apple logo appears, until you see the recovery mode screen (image of cable pointing to a laptop)
2. Once in Recovery Mode, you will see a prompt in Finder/iTunes:
- Choose "Update" first — this reinstalls iOS without erasing data
- If Update fails after 15 minutes, go back to Recovery Mode and choose "Restore" instead
- Note: Restore will erase all data on the iPhone, so only use it if Update fails
3. If Recovery Mode does not work — try DFU Mode:
- With the iPhone connected to a computer:
a. Quickly press/release Volume Up
b. Quickly press/release Volume Down
c. Hold the Side button for 10 seconds (the screen will go black)
d. While still holding Side button, also hold Volume Down for 5 seconds
e. Release Side button but keep holding Volume Down for another 5 seconds
- The screen stays completely black in DFU mode
- Finder/iTunes will detect it and you can proceed with a restore
4. If the boot loop returns after a successful restore:
- This may indicate a hardware issue (e.g., a failing battery or logic board issue)
- In this case, visit an Apple Store or Authorized Service Provider
- Check if the device is under warranty: View Coverage - AppleCare & Warranty
Important: If there is important data on the phone that has not been backed up, a data recovery specialist may be consulted before doing a restore.