iPhone iOS 4.2.1 Jailbreak Instructions (Redsn0w)

Now that redsn0w has been updated to jailbreak iOS 4.2.1 you may be wondering what's involved in actually jailbreaking your iPhone. Here are some tips and instructions to help. First of all, if you have an unlocked iPhone don't update your device to the official iOS 4.2.1 or use the redsn0w 0.9.6b4 jailbreak. You will lose your unlock.

UPDATE: Comex has released an easier method for newer 4.x firmwares. Click here for instructions on how to use JailbreakMe 3.0 to jailbreak your device.

Always back up your SHSH files before jailbreaking. This will preserve your ability to downgrade in the future. You must also find out if a tethered jailbreak is necessary on your device.

1. To see if you can jailbreak untethered find out if your iPhone is an MC model. All iPhone 4 models currently require a tethered jailbreak. If you don't want to have to boot your iPhone tethered every time you turn it off, then wait for Dev-Team to develop an untethered solution.

2. Ready to jailbreak? Download the redsn0w 0.9.6b4 software from iPhone Dev-Team. Install and run redsn0w.

3. Use redsn0w to select the IPSW file matching the current iOS version installed on your iPhone. You may want to make a backup of this file before jailbreaking, otherwise an official version can be downloaded later if necessary. These firmware files are stored in a directory on your computer. If you can't see the files in Windows make sure Windows is set to show hidden files. Here are example files:

iPhone 4 running iOS 4.2.1: iPhone3,1_4.2.1_8C148_Restore.ipsw
iPhone 3GS running iOS 4.2.1: iPhone2,1_4.2.1_8C148a_Restore.ipsw
iPhone 3G running iOS 4.2.1: iPhone1,2_4.2.1_8C148_Restore.ipsw

4. Redsn0w will verify the firmware file and prepare jailbreak data.

5. Select the check box next to Install Cydia and click Next.

6. Make sure your iPhone is plugged into the computer and TURNED OFF then click Next.

7. Follow the on-screen instructions carefully to put your device into DFU mode. When the iPhone enters DFU mode redsn0w will proceed to install jailbroken firmware.

8. Redsn0w will notify you when your jailbreak is complete. If you need the tethered jailbreak on your model iPhone, make sure to immediately boot tethered before using your device, otherwise Cydia and jailbreak apps will not work.


ispw? everytime i run redsnow it says it doesnt auto connect for 3g? i have no clue what an ispw is or how to look for one or how to get passed this part of redsnow???? PLEASE HELP!!!!! is there something more i need to download i have already set my computer to show hidden files and it didnt work... i have no clue what and ispw is or where to find it in my computer ): please help me! please direct answers to me so i know your answering my problem thanks (:

Well, I did what I was supposed to, I'm pretty sure. But Cydia won't open, and now my Safari shuts down before I can open any pages. If somebody could give me some feedback on what I need to do to rectify this problem, I would be eternally thankful. :)

thank you thank you thank you so much very helpful tutorial !

Hey guys

I don't understand exactly the text in the first para of the above page. "First of all, if you have an unlocked iPhone don't update your device to the official iOS 4.2.1 or use the redsn0w 0.9.6b4 jailbreak. You will lose your unlock.

What does it mean by lose your unlock. I have an unlocked phone from Maxis Malayisa & have beemn using in SIngapore for M1. Now I want to jailbreak with redsnow. Will the jail break happen or not?

Pls suggest?

Did this on my iPod Touch from my Macbook. Worked perfectly :D Thanks so much.

1. Got a iphone 3g my daughters old phone
2. it's unlocked to any sim
3. Want to jailbreak it
4. 4.2.1 + modem firmware 05.15.04
5. Above it has this d/load( iPhone 3G running iOS 4.2.1: iPhone1,2_4.2.1_8C148_Restore.ipsw )
6. So what do i do to get on with jailbreaking this mad iphone as it wont even back -up in itunes.
7. When i plug - in a file pops - up with 6.7 gig used data then in itunes it will say syncing 1/3 so 2 hours later no further forward.
8. I think my daughter has reset the iphone instead of backing up in itunes first then reset it, so it's all jammed - up and cannot even put my songs on this crazy iphone
9. I t works fine and is worth a Jailbreak but im a noob to this jailbreaking amazing idea.
10. From what i gather if i can change it to a ipad 2 firmware to access Cydia ect...
11..... Lastly please can some one do what i have done 1-10 on how to over come this demon of a iphone aaaarrrrggghhhh !!!

when you download the file with IE and it downloads as a zip file that's fine just change the name of the file at the end backspace .zip and add .ipsw and it immediately works like it should and converts it to work with iTunes and redsnow.

Thanks for this but I'm having trouble following the steps good thing I found this steps in WWW.JAILBREAKHOM­­E.COM I was able to jailbreak now to ios 6.1.2


Works! Took several attempts, though. NEVER, I mean NEVER release the home button in the end sequence, and do not select anything extra from the menu, they have options to choose, before the actual weird button mashing sequence! Thanks!