iPhones and iPads are pretty good at recovering automatically when they experience issues. Still, there are times when they need a helping hand. We’ve talked before about some basic troubleshooting steps for when your device won’t power on—performing a hard reset and restoring iOS itself—but the final step on that troubleshooting journey, when nothing else works, is the Device Firmware Update (DFU) mode.
Whether you’re jailbreaking, dealing with an expired beta version of iOS, or have just fallen afoul of that latest software update, you might find yourself in a position where your iPhone or iPad refuses to respond. For those situations, getting your device into DFU mode and then performing an iOS update or restoration via iTunes might be your only recourse.