These days, Apple stops signing iOS versions very soon after updates are released, so you have a short window to downgrade. The version of iOS being installed still needs to be signed by Apple, but that’s the only requirement. That’s because the iBoot bootloader will only let you install the most recent version of iOS for your device (that is, it only allows higher version numbers than what’s on the phone already). For instance, if you are running a beta of a new version of iOS, you cannot downgrade through a Settings toggle or hooking up to a computer. The other main use for DFU is to downgrade to an older version of iOS. This is done by accessing DFU Mode, and then hooking it up to a Mac or PC to install the new software. One is to repair an iPhone or iPad that has a corrupt bootloader. Apple would really rather you not muck around in this mode. Confusingly, it uses the phrase “recovery mode,” although that’s a different thing. What it looks like when an iPhone in DFU Mode is hooked up to MacOS (Catalina and later). Because it works at a lower level than Recovery Mode, DFU lets you do things not allowed in Recovery Mode. Unlike recovery mode, which can be updated with a software update, DFU is burned into the hardware, and cannot be altered. Even when you reach DFU Mode, the screen remains blank. As its full name- Device Firmware Update Mode- suggests, the mode is used to update the actual firmware of the device, mostly to install a boot loader.ĭFU Mode is hard to enter, requiring convoluted sequences of button presses to enter. It lets an iOS device connect and talk to iTunes (or its Finder equivalent in macOS Catalina), without loading the bootloader, or iOS itself. You’ll know you’re in Recovery Mode because you’ll see a graphic telling you to hook the iPhone up to a computer, in order to complete the recovery.ĭFU Mode is more powerful than Recovery Mode, and is unsupported and undocumented for us, the end user. Recovery Mode is the officially-supported way to recover your iPhone, and it is easy to reach once you know the right steps to follow. Recovery Mode is easy to get into, if you have a computer and a Lightning cable nearby. And importantly, the Recovery Mode can be patched and updated by Apple when necessary. Because it is using the iPhone’s bootloader, it can still make sure you don’t install any unauthorized software onto the device. iBoot, then waits for you to do the rest. Recovery Mode puts the iPhone into a state where it can be plugged into a Mac or PC, from which you can push a fresh version of iOS onto the device. DFU vs Recovery Mode: Which One Do You Need? From there you can reinstall iOS, or carry out other rescue operations, as detailed below. Both of these are activated by tapping out a combo of button presses on the handset itself right after powering it up, and both are designed to let you hook your dead or malfunctioning iPhone up to a computer via USB, even when the iPhone won’t boot into iOS. In order to jailbreak an iPhone, for example, you have to crack the boot loader so you can load a modified version of iOS.īut what if the iPhone won’t start up at all? In that case, there are two options: Recovery Mode, and DFU, or Device Firmware Update Mode. The bootloader is important, because it governs what can be loaded on the device, enforcing Apple’s rules and security restrictions. One of these is the loading of the bootloader, called iBoot, which in turn loads iOS. That seemingly simple procedure obscures several other processes happening in the background. A short while later, the iPhone is up and running, asking for your passcode. When you power on your device, the Apple logo usually appears. A quick note: wherever we refer to an “iPhone” or “phone” in this post, you can also assume it applies to an iPad. Here’s what DFU Mode is, what it’s really for (and not), and how to get into it. And yet this obscure tool is essential for resurrecting a dead iPhone, or rolling back an unwanted iOS update. It’s hard to activate, and the screen stays blank when you finally manage to trigger it. The DFU Mode in iPhones and iPads is an emergency tool that’s not designed for most people to ever see.
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