To begin, you'll need to get your hands a valid iOS 9 firmware (IPSW) file. This can be downloaded from the Apple Developer Center if you're a registered developer.
To upgrade to iOS 9 without a UDID registered in the Apple Developer Center, press and hold the Option key (Shift for Windows) and click 'Update' or 'Check For Update' in iTunes. Select the iOS 9 IPSW file you downloaded earlier from the popup window to install iOS 9.
- Do not do this if you want to retain your jailbreak. You will not be able to downgrade to a jailbreak-able firmware.
- Do not do this if you need to hacktivate. You must be able to activate your iPhone using a valid SIM card for this trick to work.
- iOS 9 is for developers, so if you're not a developer, we recommend holding off.
- Apple could block this loophole at any moment, so use at your own risk.
Upgrade at your own risk.
- Please backup your device before you try this!
- You MUST use the update button NOT the restore button.
- Make sure your device is activated before clicking update. We recommend turning off Find My iPhone as well.
- If you would like to downgrade back to iOS 8, we've provided instructions on how to do that here.
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