Jailbreak iOS 4.2.1 Guide for iPhone 4.2.1, iPod touch 4.2.1, and iPad 4.2.1
If you’d like to jailbreak iPhone 4.2.1, iPod touch 4.2.1, or iPad 4.2.1, you can do so by following the guide below. Currently the only tool that supports iOS 
4.2.1 jailbreak right now is redsn0w (by iPhone Dev Team).
The other jailbreak tools: greenpois0n (by Chronic Dev Team), and limera1n (by Geohot) haven’t been updated to support the jailbreak for iOS 4.2.1 yet.
IMPORTANT: We recommend that only iPhone 3G, and older iPod touch users jailbreak. This jailbreak is only untethered for the older iOS hardware. All of the newer devices are tethered, meaning you will need to re-jailbreak each time you reboot your iDevice. If that is fine with you, then go on and jailbreak.
- Download iUserbar new – click here (works on Firefox, Internet Explorer, and Safari)
- In iUserbar new, click the “Downloads” button and then click on your iOS 4.2.1 firmware to download it.
- In iUserbar new, click “Downloads” and click on Download redsn0w to download redsn0w.
- Now open redsn0w, and click the Browse button.
- Locate your device’s IPSW file that you downloaded in step 2 and click Open.
- The redsn0w window will have the “IPSW successfully identified” message. Click the Next button to continue.
- redsn0w will ask you to “Please select which options you would like to have“. Make sure the Install Cydia box has a check on there and then click Next.
- redsn0w will ask you to make sure your device is both OFF and PLUGGED IN to your computer. Make sure you plug in your device in to your computer and then turn it off. Click Next once you have done this.
- redsn0w will now ask you to connect your device in DFU mode.
- Hold down the Power button for 3 seconds
- Without releasing the Power button, also hold down the Home (bottom center button) for 10 seconds
- Without releasing the Home button, release the Power button BUT KEEP holding the Home button for 30 seconds
- If you don’t do this properly you will get a DFU Mode Failed message and you’ll have to go back to step one.
- Once this process is complete, your device will restart and it will have the Cydia icon!
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113 Comments
HELP!! i was a trying to do the reboot to activate cydia and something went wrong and my ipod went complete brick. wont even show the apple logo after holding the power button or holding the home and power at the same time. itunes wont even recognize the device. anyone have any ideas on how i can fix it?
Btw I am not the website admin. Try both recovery mode.
Hold down both HOME and SLEEP/WAKE buttons for 8 seconds, then simply releasing the SLEEP/WAKE button while still holding the HOME button for another 8 seconds. Then, whiles still holding the HOME button, plug it into your computer.
If that doesn’t work, I would try downloading software to force it to reawaken. Just google that. If nothing else works, then you are one of the less than 1% of people who cannot get out of a bricked state. Sorry about that. Ive been there.
Try different combinations of holding down the power and home buttons. I did that and it eventually showed the apple logo and turned on.
i did as said in the instructions, but i got stocked, when i clicked my iOS 4.2.1 firmware (iphone 3g one) it didnt appear anything (no links)… HELP!
OMG , it doesnt work after i finished all steps . “Cydia” was shown on my iphone , but when I open it , it doesn’t show anythings . HELP ME !!!
After you go through the install, you have to start over and just boot tethered. It will give you the instructions, step-by-step. At the end of the boot tethered, hold the Home button, until it finishes starting up. You will see the Pwnage Pineapple, instead of the Apple.
hey bob,after you install the jailbreak, you need to re-run redsn0w one more time checking the “just boot tethered right now” option. After that it should work.
same here,
iphone 4 base 4.2.1 cydia is there but crashes within .5sec of starting. please help
Btw I am not the website admin. Try the process again. It should work this time.
yeah mine, has the cydia app, but it wont open. help. im scared.
I have 3gs 4.2.1 model MC135LL serial 86001….I’ve tried with redsn0w 0.9.6b4 4.2.1 firmware and go thru steps, it freezes while exploiting. Ive also tried on my laptop and then iPhone won’t power back on.
I have also confirmed that this does not work.
You will get through all steps butt Cydia will immediately close when you try to open it even after restart.
It’s unfinished just wait for greenpois0n or limera1n release
actually just reboot tethered using redsn0w again and cydia and everything will work
i cant jailbreak my ipod touch on limera1n i do everything it tells me than it says your done and blah blah blah but when i turn on my ipod its still not jailbroken ughhhhh
HELP ME PLEASE
I downloaded the jailbreak and tried to jailbreak my iPod Touch 4.2.1 and couldn’t get cydia to open. Then I read the instructions given and it worked perfectly well. I believe if you first read and UNDERSTAND the instructions you will find that everything is fine. I now reboot and download unbelievable apps with my iPod Touch and love it. Thanks Dev Team you guys rock!
I got all the way to “wait to reboot your device” and nothing happened. The loading bar was frozen. Any help?
Ok I stand corrected it works
After you jailbreak DO NOT run cydia yet
reboot with the tether from redsn0w then run cydia
Fixed all my issues this indeed works properly they just forgot to explain that part :D
I give this a 4/5 stars i LOVE IT!!!
do not try it on 4.2.1 as stated above. when jailbreaking on 4.2.1 at this moment there is only one solution while using Redsn0w: check the box besides the following line “Just boot tethered right now” after doing this jailbreak make sure the battery isnt fully drained or else you have to redo the “Just boot tethered right now” (this also counts when installing tweaks that needs a reboot!)
Use at own risk! If you get moody/cranky while using this type of jailbreak then thats your own problem ;-)
Hello. I was going fine with my 4.2 jailbreaked phone with redsn0w but I have the bad idea of reseting my device in adjustments and data. Now it is dead, i can’t re-jailbreak it. I have no backup with cydia.
any ideas ?
thanks
need somw help with 3g got stuck on the logo i tried to jailbreak again and again does everyting right reboots 2 time and then gets stuck on logo or hoe do i restore and try again please help
Quote:
“Ok I stand corrected it works
After you jailbreak DO NOT run cydia yet
reboot with the tether from redsn0w then run cydia”
This worked after about this 3rd try. Thx