What is DFU Mode?

In this article, I would like to explain what DFU mode is and how you can easily put any iPhone to DFU mode. This will also serve as a reference for myself or any employee’s to use.

In order to understand what DFU mode is on the iPhone? We need to understand how the iPhone works, especially how Apple’s secure boot chain works to prevent loading anything that is not signed by Apple.

  1. Boot ROM, which is embedded within the processor of the iPhone contains a public key that is required during the power-up of the device. The public key is then used to verify with a low-level Boot-loader that has been signed by Apple before allowing the device to load.
  2. Boot-loader, contains a piece of code that is run whenever the different hardware circuits are getting power, on the logic board. There are two factors here LLB (Low-Level Boot-loader) and iBoot. LLB which is the lowest level boot-loader runs several firmware checks and verifies IOS Kernel signature. If this verification fails the device goes to Recovery Mode that is visible on the screen saying “Connect to iTunes”, however if LLB or iBoot fails to verify IOS it will automatically put the device in DFU.

DFU Mode

DFU stands for Device Firmware Update. As the name suggests, In the DFU mode we can flash, not only iOS but force flash iBoot/iBSS (iBoot Single Stage) and bootloader as well in case of iBoot corruption. Since in recovery mode the iBoot/iBSS only gets flashed when the version is different to what it already has.

  • When the device is in DFU mode the screen will be black, if you see anything on your screen at all, that means it’s not in DFU mode.
  • When the phones in DFU mode, iTunes will tell you the device is in recovery mode, and thats technically incorrect (but thats ok) if your device screen is all black – it is in DFU mode. However, if you are not sure and want to confirm what mode its in, you can use 3uTools which will give you an accurate status.
  • You can enter and exit the DFU state easily without breaking your device.
  • You cannot upgrade iOS and retain your data on the device as done in normal recovery mode in DFU. That is technically not true where 3uTools is concerned, as you can use the retain user data option. What that does is use the update ramdisk in place of the erase ramdisk. You can do the same thing in iTunes with a modified iPSW. You modify the buildmanifest.plist to reference the update ramdisk instead of the erase one, then perform a restore as usual with the recompiled iPSW. There was a python script that does it for you called make-no-erase-ipsw

Recovery mode

Recovery mode is designed to update and upgrade iOS whenever you do update or upgrade iOS via iTunes or via the settings, the iPhone enters recovery mode before doing the update and upgrades (Even though you don’t see the recovery mode on your iPhone. Recovery mode is only seen on your iPhone when you manually enter to recovery mode or the iPhone goes automatically to recovery mode due to some fault in the firmware) In recovery mode it is essentially keeping all your data if you choose to do an update it is installing the firmware.

How to put iPhone to DFU

iPhone 5 – iPhone SE

  • Connect the lighting cable to your iPhone and computer.
  • Hold the power button and home button till the screen goes black.
  • Then count to 2 seconds and release the power button while holding the home button.

Congratulations, you are in DFU mode, to get out of the DFU mode. Hold down the power button and home button together for 10 seconds and you should be back to normal.

iPhone 6 – iPhone 6S

  • Connect the lighting cable to your iPhone and computer.
  • Hold the power button and home button till the screen goes black.
  • Then count to 2 seconds and release the power button while holding the home button.

Congratulations, you are in DFU mode, to get out of the DFU mode. Hold down the power button and home button together for 10 seconds and you should be back to normal.

iPhone 7

  • Connect the lighting cable to your iPhone and computer.
  • Hold the power button and volume down button till the screen goes black.
  • Then count to 2 seconds and release the power button while holding down the volume down button.

Congratulations, you are in DFU mode, to get out of the DFU mode. Hold down the volume down and power button together for 10 seconds and you should be back to normal.

iPhone 8 & iPhone X

  • Connect the lighting cable to your iPhone and computer.
  • Volume up (Press one time)
  • Volume down (Press one time)
  • Hold the power button for 9-11 seconds the moment the screen goes blank.
  • Let go of all buttons for a split-second.
  • Then hold the volume down and the power button for 5 seconds.
  • After 5 seconds release the power button and keep holding down the volume down button till iTunes recognizes the iPhone in DFU mode.
  • Worth mentioning, for anyone who does microsoldering, Hydra devices, so iPhone 8 onwards, actually have a FORCE_DFU test point. In the case of the worst corruption, you can inject 1.8v into that test point prior to connecting cable, which forces DFU. We recommend you solder a magnet wire to the test point and inject 1.8v from your DC Power Supply, as soon you connect the Lighting cable to the iPhone using the output on and off button on your DCPS cut the voltage.

Congratulations, you are in DFU mode, to get out of the DFU mode. Volume up (Press one time) and volume down (Press one time) then hold the power button till you see the Apple logo on your screen, and you should be back to normal.

Credit: MobileMend UK