How to Downgrading iPhone Software?

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iTunes sports a feature that allows users to downgrade their software, so if you wind up with an iPhone running software that hasn’t had a jailbreak written for it yet, you can usually downgrade to the latest breakable version. The instructions here have been tested with iTunes up to version 7.5. It’s possible that newer versions of iTunes may remove or change this feature, but so far, there have been no signs from Apple that this will happen. In the event that it does, running an older version of iTunes might work.

To downgrade the iPhone’s software, you’ll first need a copy of the older version. Ideally, you’ll want to get a copy of whatever the newest, breakable version of the software is, based on the versions supported by the applications in the previous Post “How you jailbreak our iPhone?” These can be downloaded directly from Apple’s distribution servers, but you’ll have to know the URL. The web site http://iphone.unlock.no maintains a list of up-to-date download links for all versions of the iPhone firmware.

You’ll also need a copy of the latest iPhone Utility Client (iPHUC) available in the “downloads” section of the iPhone-Elite site at http://code.google.com/p/iphone-elite/ . The iPhone Utility Client is a tool for performing low-level functions on the iPhone, such as booting out of recovery mode and sending device firmware updates, used in the instructions to follow.

Note : The downgrade process restores your iPhone to a factory state, so any saved messages, recent calls, or other data will be completely erased. Be sure you’ve synced and backed up your contacts and calendar. Be sure to use the Image Capture utility to import any photos you’ve taken.

Perform these steps to downgrade to the older version you’ve downloaded:

  1. Connect your iPhone to the dock and start iTunes. If it syncs on connect, wait until it has finished syncing.
  2. Extract the contents of the iPhone firmware file you downloaded earlier. The file will have an .ipsw extension, but it is actually a .zip archive. You can use unzip from the command line, or your favorite graphical archival utility.
  3. Locate the file in the archive beginning with WTF, for example, WTF.s5l8900xall.RELEASE.dfu . This is the file needed to place the iPhone into a device firmware update mode. Copy it into the same directory as your iPHUC tool.
  4. Launch iPHUC from a command line. Type enterrecovery and press Enter. This will put the iPhone into recovery mode.
  5. Quit iPHUC and then re-launch it. The available commands will have now changed. Use the filecopytophone command to send the WTF file to the iPhone. For example, filecopytophone WTF.s5l8900xall.RELEASE.dfu . Press Enter. Now type cmd go and press Enter again. This will place the iPhone into “device firmware update” mode.
  6. Launch iTunes. You will be given the message that an iPhone was discovered in recovery mode. If you’re on a mac, hold the Option key and click Restore. If you’re on a PC, hold the Shift key and click Restore. You will be presented with a file selection window. Locate and select the .ipsw file you downloaded.
  7. Your iPhone will restore back to the version of the firmware 7. you’ve chosen.
  8. After the iPhone has finished restoring, you may receive an error 1015. If this happens, the iPhone will boot into recovery mode. To fix this, use the iPHUC client once more and issue the following commands (be sure to escape the spaces as shown below):
cmd setenv\ auto-boot\ true
cmd saveenv
cmd fsboot
cmd bootx
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