Rolling back your iPhone 3G to OS 3.1.3

Friends who know what I do for a living occasionally contact me with their technology problems. Take this one from my friend Margo:

I installed iOS 4 on my iPhone 3G and I hate it. It’s really slooooow and the screen acts like it’s numb. Plus, it takes forever for it to respond or react. Is there any way I can uninstall OS4 and go back to what I had? This sucks and I won’t be able to upgrade until next May.

After commiserating a bit with suggestions of deep breaths, I scoured the Web and came up with this nicely put-together Lifehacker article. I encouraged her (and now you) to read the article and comments. In the meantime, here’s the gist for downgrading the iPhone 3G (not the 3GS):

1. Locate or download a copy of the iPhone OS 3.1.3 .ipsw file. The Lifehacker story points to sources.

2. Put your phone into Device Firmware Update (DFU) mode. (Plug in the phone, turn the power off, press and hold Sleep/Wake and Home buttons for 10 seconds, let go of the Sleep/Wake button but continue to hold the Home button for 10 seconds. iTunes will then indicate that the phone is in recovery mode.)

3. Select the iPhone in iTunes’ Source list. Hold down the Option key and click Restore. You’ll be prompted to choose a file to update from. Navigate to the 3.1.3 .ipsw file and click Choose.

4. You’ll likely see an error message on your Mac and the phone will ask that you connect to iTunes. Download a copy of RecBoot. In the RecBoot package you’ll find the RecBoot Exit Only application. Launch it and use it to compel your iPhone to leave recovery mode.

5. Your iPhone should now boot to the Home screen. Restore it from a backup in iTunes. At this point it should be running the 3.1.3 software.

All good advice, but here are the caveats:

• It’s been reported that these instructions don’t work with the iPhone 3GS. Modmi.com has an entire forum devoted to downgrading the 3GS.
• Margo did this with a Windows machine and had nothing but trouble. (It’s been said that Windows users have more difficulties because, well, they’re using Windows.) She never could move her phone to 3.1.3 and so restored it back to iOS 4.
• When she did, she found that it performed far better than when she first upgraded to iOS 4. Given that, if you have a slow iPhone 3G running iOS 4, it might be worth your while to restore it again. Good things may happen.
• And, of course, this is completely unsupported by Apple. If The Bad Thing happens, expect no help from Apple (or me). You should be able to restore it back to iOS 4 as Margo did. But there’s always the (small) risk that you’ll brick the phone. So, think before you try this.