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.


FYI.......In Step 3 - When you download files, ensure you use firefox. IE has a tendency to make those file a .zip file which they should NOT BE. IT should be one file, not multiple folders!!!

thank you! That really helped! I was using IE this whole time and I was like, what the?? haha

LOL! same here! i almost asked a mate to bring his Mac round!! X)

I tried resetting network settings, uninstalling and reinstalling the GPS apps ( Navigon and Magellan ), and nothing has worked. I then decided to start from scratch – restore 4.2.1 firmware, and re-run redsn0w , but that also didargan oil
not work and left me in an even worse position, now the phone is stuck in recovery mode since the restore failed ( error 1015 ). I don’t have access to a mac, so I can’t use pwnage tool to make a custom firmware to restore to.

final solution for iphone 3g with app installation successfully

install ios 4.2.1 is final version install using

snowbreeze (follow steps in snowbreeze and finally it make new .ipsw ios
file , now install that .ipsw(ios file) using itunes )


than now for **sim card**
from cydia->install ultrasnow

+ cydia->add cydia.iphonecake.com as add resource


than search from cydia "Appsync" for ios 4.2(this is similar to ios version)--------- this is important step bcz without it no app are installed

---in above Appsync is important bcz without this no app allow to installed----

=.= juz rename it...i always do that

yeah, but all you need to do is change the file extension.

Here is the guide in German: www.beirut-entertainment.de

Here is the Guide in the German Language www.beirut-entertainment.de

Mine keeps freezing at the very first part when it says uploading ramdisk. What the hell

I had this same issue, not able to get any farther anyone have any tips?

Restart the Jailbreak,click cancel and redo the steps CARFULLY,I had this problem when i Jailbreaked my iTouch!

I keep repeatedly having this problem, followed all instructions as carefully as possible, but once it gets to "Uploading ramdisk" it won't seem to go any further, first time it immediately went to 5 blue bars, but no further, then 10, the second time and 9 the third...
Am I just not waiting long enough or is it not going to go up anymore?
How can I get it to continue?

Anyone still having this problem? I got stuck at 2 bars on the first try. And then 1 bar on the second try. Waited for 30minutes and still nothing happened.

i am having this same exact problem. did you ever get a fix for it? i am a bit of a jailbreaking noob, and i cant seem to find an answer for this problem

i know how to fix that, at the part where your holding down only the home button, DO NOT LET IT GO UNTIL IT IS COMPLETE TO INSURE BETTER PROGRESS, though i got a problem myself... ONCE IT LOADS IT GOES TO FROZEN RESTORE ITUNES CRAP AND USING OTHER STUFF WHILE IN IT DOESN'T WORK EITHER

download everthing from firefox and follow the instructions & dont change nothing or add nothing when it gives you the option to enable multitasking, wallpaper ect. leave it like it is ....i had the same problem when i would enable multitasking & wallpaper so i tried again & this time without changing anything it worked :)

verry pissing offf

make sure u run as admin, get it from here http://www.kittyra1n.com/jailbreak-and-unlock-iphone-3g-4.2.1.html

I was jailbreaking my iPhone 3G which is currently on 4.2.1 and followed all the instructions, i didnt connect my iphone to the pc n waite for the redsn0w0.9.6b4 to recognize my IPHONE3G 4.2.1 software (downloaded from felixbruns, am sure its the correct one i checked this and redsn0w a million times!! It still says UNABLE TO RECOGNIZE SPECIFIED IPSW!! Is it must to connect ur iphone while redsn0w is recognizing the selcted firmware???

check this link:

try this blog:


I have a i phone 4 running 4.2.1 mc model should i attempt this will it work as most of the comments on here are for 3gs

Please someone help m going crazy with this. My story goes like this:

I have an iphone 3gs which used to have a tethered blackra1n jailbreak on iOS 3.1.2.
I couldn't update my SHSH blobs to Saurik server as my Cydia was continously crashing.
I tried to reinstall Cydia but it would require a restart, and a restart wasn't possible as it was tethered. I would again use

Blackra1n and the same Cydia situation would come back. I accidentally put 4.2.1 firmware and try to unlock it with redsn0w. but

the phone wouldnt turn on and got stuck on apple logo. i try to tether reboot but it didnt work either. Now my phone's in recovery

mode and with installed baseband 6.15(ipad baseband). I cannot recover it back to 4.2.1 as it counters with 1015 error. I can't do

anything as the 3194 error shackles me at every step. Please help, its my friend's iphone and he will kill me if i don't do . And the iphone is New Bootrom.

anything soon.

Worked like a charm on my 3g. Thanks

cant get it to work on my 3g, it uploads files, goes through to the restart and then when the apple logo comes up, it just stays there.......starting to think this is impossible to do on a 3g

having the exact same issue. anyone know a fix?

I am not able to see my ipsw file to jailbreak my iphone 3g 4.2.1. I have set windows to show hidden files. the file says its empty. what to do now?

to see the ipsw you have to make the zip file extension to ipsw extension.
i.e chane the *.zip to *.ipsw

My story so far is sad :-(
1. I have (or had?) 3GS 4.2.1 with MC number. Tried to jailbreak with redsn0w - successful at tethered boot. Then tried to unlick it through cydia. after this all it was showing was a 'bitten apple' sign on the screen. It was not able to boot..
2. Then connected to iTunes in recovery mode, it mandates latest OS upgrade, just did it (unfortunately!) the upgrade terminated unsuccessfully saying " error 1015" guess that is because the redsn0w ipsw. now it is showing "connect to iTunes" sign always and not booting..HELP..I don't want it to turn brick!!