Whether you want to jailbreak, un-jailbreak, update from an expired beta, or simply update when nothing else is working, putting you iPhone or iPad into DFU (Device Firmware Update) mode can be your last, best hope for success.
DFU mode, as opposed to Recovery Mode, requires a bit of timing and can take practice to get right, so if at first you don't succeed, don't be afraid to try and try again.
How to put your iPhone or iPad into DFU mode
- Plug your iPhone, iPod touch, or iPad into your Mac or Windows PC and make sure iTunes is running.
- Hold down both the Sleep Button (on top of your device) and the Home Button (on the front underneath the screen).
- Keep them both held down from about 10 seconds. (If you see the Apple logo, you've held them too long and will need to start again.)
- Let go of the Sleep Button but keep holding the Home Button for about 5 seconds. (If you see the "Plus into iTunes" screen than you held it too long and will need to start again.)
- If the screen stays black, that's it! Your iPhone, iPod touch, or iPad should now be in DFU mode.
At this point iTunes will show you an alert saying it's detected your iPhone, iPod touch, or iPad and it needs to be restored.