[How To] Downgrade iOS 4 to iPhone OS 3.1.x

In the excitement of upgrades and a whole new slue of jailbreak tools, many people are slowly realizing that they are not yet ready for iOS 4 for various reasons, wether it's a new bootrom or just simply missing a favorite jailbreak app from Cydia. This guide will help you downgrade your recent update to iOS 4 back to 3.1.x. While it is highly recommended to restore to 3.1.2, not everyone has that option, but only use 3.1.3 as a last resort. It is important to note that if you are downgrading, in order to upgrade to a jailbroken iOS 4, you MUST be on 3.1.2. The only jailbreak for 3.1.3 is Spirit, which is currently NOT compatible for upgrading to a jailbroken iOS 4. Before we even get started, you must have your SHSH blobs on file with Saurik's server. You can check this by opening Cydia and seeing a message similar to this one:

If you are 100% sure you have this message, and recall choosing the "Make My Life Easier" option when you first launched Cydia, then it's time to proceed. If you unfortunately do not have these saved, and are already on iOS 4, then there is nothing you can do.

Ok, so you made it past the first step. You have SHSH blobs on file via Saurik's Cydia server, which means your going to be able to downgrade just fine. The next question is, which firmware would you like to downgrade to. In my case, I don't have SHSH blobs on file for 3.1.2, so I will be downgrading to 3.1.3 instead.

Grab your stock firmware from the links provided at our download page. Make sure you are using the one you have SHSH blobs on file for.

How To Downgrade iOS4 to iPhone OS 3.1.x:

Note: This guide ONLY applies to the 3GS

Step 1:

• Modify the Hosts file

In order to trick iTunes into connecting to Saurik's server instead of Apple, we need to modify the hosts files. This applies to both Windows and Mac users. By doing this, we are able to get iTunes to think that our device is eligible for a downgrade. Normally when a new firmware is released, the older firmwares are no longer signed by Apple, thus preventing downgrading, but by connecting to Saurik's server, we bypass this issue.

1a: Modifying Windows Hosts file

• Browse to Windows\System32\drivers\etc\. Inside this directory you should be able to find a file named "Hosts". Open this in Notepad and add the following " 74.208.10.249 gs.apple.com " line to the bottom as shown in the screenshot.


• Due to some restrictions on Windows you may have to create a copy of this file on your desktop and then drag and drop it to replace.

1b: Modifying Mac Hosts File

• The same idea as windows here, only in a different location. On your Mac, Open Finder, and choose Go from the toolbar, and then Go To Folder. Type in the following: etc/ .

• This folder should pop up, and inside you'll see the hosts file. Open this file with textedit and add the following " 74.208.10.249 gs.apple.com " line to the bottom as shown in the screenshot.


• Save the file.

Step2:

• Install Firmware Manually

• Now you can launch iTunes, shift click, or ctrl click, Restore, choose your firmware, and the downgrade begins. Some of you may not have any problems from here, but some of you will end up in recovery mode by the end of it. Do not worry, this is normal. Now we just need to force the phone out of recovery mode.

Step3:

• Fix Recovery Boot Loop

In our case, I used iReb to easily fix the recovery boot method. This is of course on Windows, but you can also use many of the methods out there to fix the recovery loop. If you need further help with this, post a reply.

Step4:

• Welcome Back to 3.1.x.

That's it! That is all you will need to do to get your iPhone OS back to 3.1.x, where you can safely wait for further development of iOS 4 from both Apple and the Jailbreak community developers before hopping the bandwagon. Don't forget to stay tuned for more jailbreak and unlocking news by following us on Twitter and/or subscribing to our RSS feeds.