What is DFU Mode?
DFU stands for Device Firmware Update. DFU is all about upgrading your device. For instance, when Apple released iOS 6, you could either do an OTA update or do a manual update by downloading the firmware yourself. In the latter, you would use DFU mode to upgrade the firmware.
Why You Required to Put iPhone into DFU Mode?
DFU mode is where the bootloader is mounted and the iPhone/iOS device gets ready to upgrade its firmware. DFU mode is often required when you are doing a manual upgrade using custom IPSW files. This comes in handy especially during those jailbreak sessions.
How to Enter iPhone or iPad into DFU Mode in iOS 8 or Earlier iOS Version:
Entering your iPhone in DFU Mode is pretty simple. Most jailbreak tools like Redsn0w even guide you through the processes pretty smoothly. (Note: If you own iPhone 7 or iPhone 7 Plus, here is how you can put it into DFU mode.) Here's how it's done:
Step 1: Connect your iPhone or iPad with your PC or Mac and make sure iTunes is running
Step 2: Switch off your iPhone by holding Power button and slide to power off
Step 3: Hold the power button for 3 seconds
Step 4: Press and hold the Home and Power (sleep/wake) buttons for sometime (10 seconds)
Step 3: After this, release the Power button but keep the Home button pressed for 15 seconds
Step 4: This puts the iPhone in DFU mode. The screen remains black.
Step 5: When you connect your iPhone to iTunes, a popup tells you that iTunes has detected an iPhone in DFU mode.
Typically, if you're new to this, you might have to try a couple of times to nail it. If, on the third step, you see the Apple logo come up, it means you have to start again because the iPhone has booted normally.
How to Get iPhone Out of DFU Mode
It is quite easy to get your iPhone out of DFU mode.
- You just have to press and hold Home and Power buttons for about 10-12 seconds
- Now, release the Home button but keep pressing the Power button till Apple's logo comes up on the screen. Your iPhone is out of DFU mode.