Internal Firmware

From The Apple Wiki

This is a documented list of Internal Firmware types:

  • InternalUI Builds, which are Development/Debug builds of *OS
  • NonUI builds, which are for Factory and Development testing of *OS devices.
  • CarrierOS, which are meant for Carrier Testing.
  • Horizon Firmware, which are stripped-down NonUI builds to recalibrate parts for iPhones.