This guide will help you perform an iOS 4.2.1 untethered jailbreak on your iPhone 4 and also unlock it if required. We will be using Greenpois0n’s latest release to jailbreak iPhone 4 using a Mac computer. Please note that Unlock is only available to iPhone 4′s at baseband version 1.59.00
What Files do you need?
- Greenpois0n – Link
- iOS 4.2.1 firmware file for iPhone 4 – Link
iOS 4.2.1 Jailbreak Procedure:
If you do not have a factory unlocked iPhone 4 and rely on software based unlock like Ultrasn0w you should be careful not to update baseband version else you will lose unlock forever. Read how to Upgrade iPhone 4 to 4.2.1 safely preserving baseband before proceeding.
Extract Greenpois0n from the archive you downloaded above and run the file.
Turn off your iPhone 4 after connecting it to your computer and press the Jailbreak button. You should now see instructions to put iPhone into DFU mode. Follow them as shown on the screen.
If you fail to do it right you will be prompted to try again. Don’t worry and give it another try patiently. In case you get it right Greenpois0n will start jailbreaking your iPhone 4.
Once the Jailbreak is over click on the complete button and wait for your iPhone to restart.
You should now be able to see a new application called Loader on your iPhone screen.
Tap on Loader and then select Cydia. Tap on install Cydia.
Once Cydia has installed tap on Remove Loader. That’s it your iPhone 4 is now jailbroken with Cydia installed. If you need to unlock your iPhone 4 read How to Unlock iOS 4.2.1 on iPhone 4 with Ultrasn0w.
If you have any questions or got stuck in any step feel free to ask us via comments.