How to Unlock iOS 4.2.1 on iPhone 4, 3GS, 3G with Ultrasn0w

How to Unlock iOS 4.2.1 on iPhone 4, 3GS, 3G with Ultrasn0w

We shared the iPhone 4.2.1 unlock with you as soon as it became live. This guide will show you how to unlock iOS 4.2.1 on any iPhone (3G/3GS/4) using Ultrasn0w. Ultrasn0w has been updated to version 1.2 and is now live on cydia.

Before we show you the process to unlock iOS 4.2.1 with Ultrasn0w, let me tell you which basebands can be unlocked currently.

Basebands supported by Ultrasn0w 4.2.1 unlock:

iPhone 3G / 3GS Basebands:

  • 04.26.08
  • 05.11.07
  • 05.12.01
  • 05.13.04
  • 06.15.04 (those stuck on 05.14 or 05.15 should first upgrade to 06.15 to unlock)

iPhone 4

  • 01.59.00

It might all sound confusing initially but don’t worry. As you read our guide you will easily make your way through.

In case you don’t know your iPhone’s firmware version or baseband version take a look at our detailed guide to find out iPhone firmware and baseband version.

In order to proceed with the unlocking you need a jailbroken iPhone with Cydia installed. In case you haven’t jailbroken yet here are the jailbreaking guides.

Ultrasn0w unlocking instructions:

Tap on Cydia from your iPhone homescreen.


Once Cydia loads, Click on the Manage button and then on Sources.



The ultrasn0w repo should ordinarily be present in the list. In case it isn’t tap on edit and then on the Add button on Top. Enter http://repo666.ultrasn0w.com as the URL and tap on Add Source. Tap on return to Cydia and you should now be able to see Ultrasn0w repo in the list.


Select repo666.ultrasn0w.com and then Ultrasn0w on the next screen.


Once you see the updated Ultrasn0w version 1.2 press Install and then Confirm.


You will be asked to reboot iPhone by Cydia when Ultrasn0w has been installed.


There you go. Insert any GSM SIM card into your iPhone now and it will be active in less than ten seconds.


You don’t need to restart the next time you change the SIM card.

Feel free to ask questions via comments, in case you have any. We’ll try helping you to the best of our abilities.

Article by Rajat

Rajat has written 225 articles.

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{ 2 comments… add one }

  • Dan

    January 15, 2011, 5:07 pm

    is it true that once I have jailbroken and unlocked my iPhone 3GS o.s. 4.2.1, whenever the battery drains completely or I shut off the phone, I will have to use a computer to reboot? Please confirm.

  • Joachim Idland

    September 24, 2011, 2:56 pm

    Dan, is you have 4.2.1 you can use greenpois0n, what is untethered and means you dont need pc to reboot, but if you installl tehtered exapmple: ios 5 b1 or .4.3.5 which isnt jailbroekn yet, you can jaul break, but tethered which means you have to use pc

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