DFU (Device Firmware Update) mode is a low-level mode for updating device firmware. DFU is used to update or restore the firmware of a device only in cases where standard tools for such an operation are no longer suitable. In some cases, this mode helps to fix a minor software failure and allows you to reload in normal mode.
To switch to DFU on iPhone 7, you need to follow the steps below:
1. Connect the device to the computer and launch iTunes.
2. Turn off the iPhone. To do this, hold down the screen lock button and shift the power switch to the right.
3. Hold the Power and Volume down buttons and hold them for 10 seconds.
4. Release the Power button, but continue to hold the Volume down until iTunes displays a message about entering recovery mode.
In DFU mode, the Apple or iTunes logo should not appear on the device’s screen - if this happened, the sequence of operations was incorrect or the input failed. In this case, you just need to repeat all the steps described in the instructions.