How to Jailbreak Your iPhone 4 Using RedSn0w (Windows) [4.2.1]

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Posted November 23, 2010 at 9:26pm by iClarified

These are instructions on how to jailbreak your iPhone 4 on the 4.2.1 firmware using RedSn0w for Windows. The Mac version of this tutorial is here.

You will only be able to perform a tethered jailbreak at this time. This means you will need Redsn0w's assistance to boot into your jailbroken device. If you want to jailbreak a lower firmware version you can find the appropriate tutorial here.

Make sure not to update to iOS 4.2.1 if you need an unlock as one is not yet available!

Step One
Create a folder on your desktop called Pwnage

Download RedSn0w from here and place it in the Pwnage folder. Likewise, download the latest 4.2.1 firmware from below and place it in the same folder.

4.2.1 (4): iPhone3,1_4.2.1_8C148_Restore.ipsw

Extract the redsn0w executable from the RedSn0w zip file into the same folder.

How to Jailbreak Your iPhone 4 Using RedSn0w (Windows) [4.2.1]

Step Two
Connect your iPhone to the computer and launch iTunes.

Select your iPhone from the list of devices on the left. Now hold down Shift and click the Restore button. Restore is preferred as it won't create any wasted space on your iPhone.

Navigate to the Pwnage folder on your desktop and select the 4.2.1 firmware ipsw. Click the Choose button to continue.

Step Three
Once iTunes has finished updating your iPhone to the desired firmware open the Pwnage folder on your desktop and launch the redsn0w application from the redsn0w folder we extracted earlier.

Step Four
Once RedSn0w opens click the Browse button

Step Five
Select the 4.2.1 firmware ipsw we placed in the Pwnage folder on our desktop then click Open.

Step Six
Once the firmware has been verified click the Next button to continue.

Step Seven
RedSn0w will now prepare the jailbreak data

Step Eight
From this window you can select the jailbreak options you would like.

Make sure Cydia is selected and click the Next button to continue.

Step Nine
Please plug your iPhone into the computer and make sure its OFF then click the Next button

Step Ten
RedSn0w will now guide you through the steps to get into DFU mode. You can find more help with DFU mode here

Hold down both the Home button and the Power button for 10 seconds.

Release the Power button and continue holding the Home button until RedSn0w detects the device.

Step Eleven
Your iPhone will now reboot

Step Twelve
RedSn0w will then begin uploading the new RAM Disk and Kernel.

Step Thirteen
Once this is complete you will be notified that RedSn0w is done. Click the Finish button. When your iPhone finishes rebooting (5 minutes or so) it will be jailbroken with Cydia on the SpringBoard.

IMPORTANT:
To use Redsn0w to help you boot back into your jailbroken device simply select Just boot tethered right now from the options window and click Next.

*As usual a big thanks to the iPhone Dev-Team for their hard work and contribution to the iPhone community.

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Mostafa - February 25, 2011 at 5:12pm

Jalbreak process is done succesfully but the iphone is not starting up.it just hangs when i turn it on...PLZ Help

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mo - February 25, 2011 at 5:23pm

why you using redsn0w use GreenPois0n alot better and easyer too.

pjaffar - February 10, 2011 at 1:51pm

I download the iOS4.2.1 from the link above and when i try to update my iphone4 to the new iOS i keep gettin the same error 1001 1002 1003 1004 error message. someone can help me fix it ?

Oskar - February 4, 2011 at 3:58am

Hello! I was succesufull jailbreak my iphone 4 (4.2.1) yesterday. But my problem is that I can not get any service from any operator. Can anybody help me?

Bill Carney - February 3, 2011 at 2:04pm

Need help, JB freezes on Uploading ramdisk

Yammer - February 3, 2011 at 2:06pm

Every time I go through the setup with redsn0w, hold all the buttons as directed, once it gets to the point where it says uploading ramdisk it just freezes. Never moves again. Sometimes on the first bar, sometimes on the fourth, etc... I can't go any further, please advise! Thanks, Yammer

www.ivancovic.com - February 2, 2011 at 4:24pm

uploading ramdisk error, just standing, please help me,,, :(

www.ivancovic.com - February 2, 2011 at 4:26pm

iphone 4 4.2.1,Firmware 03.10.01

Mickey - February 2, 2011 at 12:03pm

Can I jailbreak (factory unlocked, so don't need unlock) my iphone 3gs with 4.1.2 version with this jailbreak? Or does it have to be an iphone 4?

kevin - January 26, 2011 at 2:40pm

whats going on with this jb? i follow the instructions and get it done, but then cydia crashes and my phone reboots and all i get is the apple logo? then i have to reboot my phone, any one else had this?

Mo - January 27, 2011 at 6:53am

After any cydia update or switch your phone off and on again you must boot tethered again.once you get every thing working dont do any more update.it should work fine than.

khim - January 26, 2011 at 12:10am

hi ! i just JB my iphone 4 version 4.2.1 ~ Everything looks fine, one question.. I plug in the iphone to computer, it will not recognize by itunes ? i can't do any sync... It's normal or abnormal? please advise...

Mo - January 26, 2011 at 5:19am

No this very abnormal ,the phone should work fine with any computer you plug in. try different USB port restart you computer and last try the boot tethered again.

Thala - June 3, 2011 at 7:37am

Uinstall the latest itunes n connect it.. ur phone willbe connected with system

ankitvp - January 21, 2011 at 4:23am

i have a factory unlocked iphone4 4.2.1 03.10.01, my question is 1. if i JB it, will i loose the unlock? 2. do i hav to save SHSH using TU? 3. if in future i upgrade it to 4.3 or whatever, will i loose the unlock? Please help...too confused thanx so much

Tara - January 21, 2011 at 6:50pm

You will never lose your unlock by JB or upgrading to a new firmware (4.3 or 4.4 or any). The worst will be that you have to restore using itunes. Your iphone wil aways remain unlocked.

ankitvp - January 21, 2011 at 7:35pm

thanx!! phew!! now I can sleep in peace :)

Ridi - January 2, 2011 at 10:39am

running redsnow, step twelve is running and only fills 10-20% on iphone just standing download jailbreak data and after ~10minutes iphone reboots but redsnow doest finished the step.. whats going on?!

Mo - January 3, 2011 at 4:35pm

Make sure you using a computer with usb2 or change the USB port.give it a go than let me know.

Ridi - January 3, 2011 at 7:50pm

computer hardware is up to date and allrdy using usb 3.0 also 2.0 i'll try soon again

Mo - January 4, 2011 at 5:07pm

Sorry mate don't know what's wrong.try deferant USB port.just done one this morning it toke so many try's too.

fred - December 31, 2010 at 2:45pm

redsonw wont recognoze the ispw file running new iphone 4 4.2.1

jason - December 26, 2010 at 5:31pm

JB seems to have gone through without any problems. I click on the Cydia icon and nothing happens. I do the 'Just boot tethered right now' and I'm able to get into Cydia. If I install any program, it wont finish booting up. It hangs up with the Apple logo. At this point, I'm unable to shut it down completely so I can try to reboot into tethered again, so I have to restore it and start over. Windows 7 64x, redsn0w 9.6b4, iPhone3,1_4.2.1_8C148_Restore Any ideas?

Mo - December 26, 2010 at 6:33pm

When you finish installing cydia don't do any updates and don't restart your iPhone,you can install installus but make sure you Install the right version.

Jay - January 14, 2011 at 3:27am

same problem here!!!

meganOUFC - December 15, 2010 at 5:54am

Hi :) Jailbroke the phone fine, then installed a arsenal theme which then 'cashed' the phone , by that i mean, apple logo for ages then off then apple logog, over and over. so put in recovery mode and restored. now when i try and jailbreak the jailbreak doesnt gp further than stage 2..... waiting for reboot. so never even goes as far as actually jailbreaking the phone ( black screen followed by white writing and then pineapple logo) any help appreciated. thanks

Mo - December 15, 2010 at 4:07pm

Make sure you using a computer with USB 2.0 and make sure the iPhone is activated

MeganOUFC - December 15, 2010 at 6:25pm

Hi thanks for replying. iPhone is 100% activated and how do I know if I have USB 2.0? Thankyou

Mo - December 16, 2010 at 5:30am

When you plug your IPhone to the computer dos it say "The USB device can perform faster if you connect it to a High Speed USB 2.0 port." ??? and try it with a different usb port too this might help.

MeganOUFC - December 16, 2010 at 5:51am

It does say that actually. Just to note j have jailbroken the 3g and the 3gs as well as iPods 1st and 2nd gen no problems on this computer. I hae another latop but it's on windows 7 not xp

Mo - December 16, 2010 at 9:28am

iPhone 4 Need more power from the computer.try it with windows 7 it should be ok.

meganOUFC - December 16, 2010 at 12:38pm

okay, i'll give it a try. thanks again. hopefully that sorts it! .. i've got a question for the iphone 3g now!! over i go to that section lol!

Mo - December 21, 2010 at 7:48am

How did it go ?? did you manage to get it working?

meganOUFC - December 21, 2010 at 11:59am

well my mate wont let me near his phone now to try :/........... oh well im not worried. Now i am having trouble with my iPhone which s a 3g. why are things never easy?? lol

MO - December 21, 2010 at 12:08pm

:) i just got my iphone 4 done and working fine,its not easy and takes some time. nothing is easy in this life man :)

Mo - December 9, 2010 at 3:47pm

I have managed to jb my iphone.but every time I update Cydia it stops working and I have to restore it and do the jb again.now when I get it working again and without updating if u switch the phone off and back on the Internet and cydia don't work again.I have tried every thing but still not working.I think we need to wait for an update or new way of doing it.

MJWJ - December 7, 2010 at 8:22am

I do seem to have trouble loading the 4.2.1 JB redsn0w from windows laptop. iPhone 4 dosn't complete the reboot session, not even after an hour of processing. rebooting in tether option only doens'seem to work either. Any ideas??

meganOUFC - December 13, 2010 at 8:26pm

same here, any ideas?

Bill - December 5, 2010 at 2:19pm

This will lock your phone. It will update your baseband to the most recent, so don't do it if you need to unlock it.

Jjh - December 5, 2010 at 7:19pm

So it means if u want to unlock ur phone, do not jb or update to iOS 4.2.1 right? And btw what's unlock?

scot - January 6, 2011 at 5:01pm

how if I've updated to iOS 4.2.1? so now what can i do? Is there any way to unlock the phone now?

Jjh - December 5, 2010 at 7:47am

Hi guys! I need ur help here... What does it mean by 'Make sure not to update to iOS 4.2.1 if you need an unlock as one is not yet available!' ??? I hav updated my iphone4 to iOS 4.2.1, so does this mean that I am not able to jb my iPhone?

jayson - December 4, 2010 at 1:22pm

Hi anyone canhelp mi??? i JB my phone then the cydia icon is white in color then i restore my phone using the firmware again but i can't jb my phone again.. anyone canhelp??

ceetang - December 6, 2010 at 11:37pm

You must redo redsnow but instead of installing cydia you boot tether

iNathanL - December 17, 2010 at 4:58pm

i have the same problem but that didnt work for me :[

theduce - December 3, 2010 at 7:10am

hei guys, any ideas about why I get an error with itunes ver. 10.1 when i try to restore my iphone4 to 4.2.1..it gives me the error : the iphone "iphone" could not be restored, an unknown error has occurred (1013) . Before this I was running on 4.1 and bb 2.10.04..anyone cand HELP ?

tfg - December 13, 2010 at 12:22pm

Remove gs.apple.com from /etc/hosts. You have tutorials on the net.

bogdan - December 24, 2010 at 6:15am

Try to use another computer, especially if it has Win XP on it. Upgrade to the latest iTunes

Brazil - December 2, 2010 at 3:14pm

Hi! I tried to jailbreak Iphone 4 several times. All times I got an Apple logo after jailbreak process. I've tried so many instructions listed here and another places and no success. Can anyone help me? Thanks!

harsha - December 16, 2010 at 12:28am

me hvn the same problem dude...........my phone is also hanging at that reboot session .....if u get a solution plz let me klnow

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