Redsn0w by DevTeam allows you to jailbreak your iPhone 4 device, to get complete control over it (see why you should jailbreak here). Currently, redsn0w version 0.9.6b5 allows you to perform a tethered jailbreak to your device that has already been upgraded to firmware 4.2.1, which means you need to use redsn0w every time you boot the device, otherwise all your jailbreak data gets wiped. However, it will NOT unlock the device, enabling it to be used with different GSM carriers worldwide.
- An iPhone 4 updated to firmware 4.2.1
- Firmware version 4.2.1 for iPhone 4
- iTunes 10.1 or later
- redsn0w 0.9.6b5 for Mac.
Please backup all your information using iTunes before following this tutorial.
1. Download redsn0w and extract the ZIP. Double-click to open redsn0w application.
2. Click the ‘Browse’ button below the text, it will ask you to locate a firmware file, choose the 4.2.1 firmware for iPhone 4 and click ‘Open’.
3. It will then process the firmware file. After it says ‘IPSW successfully identified’, click the ‘Next’ button located near the bottom-right and it will download some jailbreak data from the server.
4. Then, choose if you want to install cydia and click the ‘Next’ button again.
5. Now, it will ask you to connect the device to your Mac/PC and then turn it off, do so and click ‘Next’. Now follow the on-screen instructions to proceed.
6. The device will reboot a couple of times showing ‘Downloading Jailbreak Data’ logo on the device’s screen, while redsn0w sends modified files to the device. When redsn0w is done, click the ‘Finish’ button and let the rest of process continue on the device, please be patient.
7. After it reboots, it might just go into the recovery mode. At this point, press and hold both home and power button till the screen goes off and now just press the power button to power it on. When it boots up, your device should now be jailbroken with Cydia on the homescreen.
All credit for the great tool goes to the DevTeam.