How to reboot an iPhone X

To perform a hard reboot on the iPhone X

  1. Press and quickly release the Volume Up button
  2. Then do the same for the Volume Down button.
  3. Follow up by pressing the Side button, and hold until the display suddenly shuts off — about 10 seconds.
  4. Keep holding the Side button and release when the device turns back onto its Apple boot screen.

This is the same process the iPhone 8 and 8 Plus use to force-restart, too.