If you have an iPhone 4 and want to unlock it on the iOS 5 firmware you are in luck. The Dev-Team have recently updated UltraSn0w to version 1.2.4 which supports unlocking the iPhone 4 on the official iOS 5 firmware. This new version of UltraSn0w does not support any new baseband versions and can only unlock an iPhone 4 running the *01.59.00 baseband. If your iPhone is not running the 01.59.00 baseband then you cannot unlock your iPhone 4.
*In order to see if you have baseband 01.59.00 on your iPhone 4 you will need to go into the Settings.app > General > About and look for the Modem Firmware field.
In this how to guide from iJailbreak.com you will learn how to unlock your iPhone 4 on the 01.59.00 baseband. If you have an iPhone 3GS please click here to follow our guide specific to unlock the iPhone 3GS on a number of different basebands including the special 06.15.00 iPad baseband.
Note: If you would like to unlock your iPhone 4 on the official iOS 5 firmware you must first update to the iOS 5 firmware through a custom IPSW created using RedSn0w 0.9.9b5. DO NOT update to the stock iOS 5 firmware as you will additionally update your iPhone 4′s baseband.
Unlocking iPhone 4 on official iOS 5 firmware
Step 1: You must already be running the official iOS 5 firmware on your iPhone 4 (click here if you are not), and you must also be Jailbroken on the iOS 5 firmware. If your iPhone 4 is not Jailbroken please click here.
Step 2: After your iPhone 4 is running the official iOS 5 firmware and is Jailbroken you will need to simply launch Cydia from your springboard.
Step 3: Once Cydia is up and running you will need to go into the Sources page. To go into the Sources page tap Manage followed by Sources.
Step 4: Typically, the UltraSn0w repo is included with Cydia. If not, tap the Edit button followed by the Add button and you will be prompted to add a URL source. Type:
Followed by tapping the Add Source button.
Step 5: Cydia will automatically refresh and update sources.
Step 6: After Cydia is done refreshing sources. Tap the Search tab on the bottom tab bar and search for UltraSn0w. Once UltraSn0w appears, tap on it and you should see version 1.2.4. Read through the description and tap the install button to install UltraSn0w 1.2.4 to your iPhone 4 running the iOS 5 firmware.
Note: In case you are not familiar with UltraSn0w, it is a software unlock for your iPhone 4 meaning you can use your iPhone 4 with any carrier by simply inserting the SIM card.
Step 7: When UltraSn0w is installed you must restart your iPhone 4 and run RedSn0w to boot tethered, you’re done!
With UltraSn0w now installed on your iPhone 4 you will be able to enjoy the benefits of using any carrier while running the new iOS 5 firmware. Let us know if you have any questions in the comment section below…