Symptoms

  • “The iPhone could not be restored. An unknown error occurred (4013)” during update or restore.
  • The progress bar stops partway and the device reboots to Recovery.
  • It fails at the same point each attempt.

What causes Error 4013 / 1008F

  • A worn or non-certified USB cable, or a flaky port or hub.
  • Antivirus or VPN software interrupting the USB connection.
  • Not enough free space on the Mac or PC to stage the firmware file.
  • A software fault serious enough that a normal restore cannot complete.

How to fix it

  1. Use an Apple-certified USB cable plugged directly into the computer (no hub), ideally a different port; try a different computer if you can.
  2. Free at least 15 GB on the computer and quit VPN and antivirus software, then retry the restore in Recovery Mode.
  3. If it still fails at the same spot, put the device in DFU mode and restore from there.

Terminal / CLI command

sudo purge

Optional, on macOS — frees inactive memory before a large restore. Not required.

How to confirm the fix: The restore completes to the Hello / setup screen and the device boots normally.

Prevent it from coming back

Keep a known-good Apple cable for restores, and keep 15–20 GB free on the computer you sync with.