Complete Guide: Jailbreak iOS 4.2.1 on any iOS Device with Redsn0w

November 23, 2010 — by Megha Bassi29



Complete Guide: Jailbreak iOS 4.2.1 on any iOS Device with Redsn0w

November 23, 2010 — by Megha Bassi29

redsn0w-ios-4-2-1-jailbreak1.pngEarlier today we saw Apple’s iOS 4.2 going live for all iOS devices and in less than a day’s time the Dev Team has released a Jailbreak supporting all devices. Redsn0w has been updated to Jailbreak iOS 4.2.1 and is now available for both Windows as well as Mac.

This guide will help you jailbreak any device. However, let me first warn iPhone owners relying on Ultrasn0w unlock. An unlock hasn’t been released yet for iOS 4.1 or 4.2 and it will be available only after Cydia has been updated to 4.2(in a week’s time maybe). So at the moment you should refrain from upgrading to 4.2.1 and not use this guide.

The Redsn0w Jailbreak will offer a tethered or untethered jailbreak depending on the device you own:

  • iPhone3G, older iPhone3GS, and non-MC iPod touch 2G: untethered jailbreak
  • More recent devices (iPhone 4, iPad, iPod touch 4G): tethered jailbreak (meaning if your device reboots, you’ll have to re-jailbreak)

Steps to Jailbreak iOS 4.2.1:

1. First update your iPhone to the latest firmware by downloading the IPSW file using direct download links here. Use the direct download link as you will require the IPSW file during jailbreak in the later steps.

2. Open iTunes and press Shift + Update(windows) or Alt + Update(Mac) and point to the IPSW file to update device.

3. Download latest Redsn0w for your operating system:

4. Extract and run Redsn0w.


5. Click on browse and point to the IPSW file and hit Next. Once Redsn0w has prepared jailbreak data select “Install Cydia” and proceed with the onscreen instructions.



Screen shot 2010-11-23 at 7.44.10 PM.png

6. Hit Finish once Jailbreak is over.

Screen shot 2010-11-23 at 7.44.38 PM.png

In case your device falls in the Tethered Jailbreak category, you will need to repeat the steps with “Just Boot Tethered Right Now” selected. If you don’t do this Cydia won’t work yet. For Untethered devices, the magic is all done.

For tethered devices, it is a little exhausting to repeat this process every time the iPhone restarts but at least we do have an early Jailbreak.

In case you run into an issue do feel free to leave us a comment. Happy Jailbreaking!

Megha Bassi

Megha Bassi has a strong fascination for all things Apple. Not only does she religiously follow Mac and iPhone news, but also loves writing about everything pertaining to it, be it publishing useful tutorials or app reviews.

  • Chri

    Tethered is lame

  • Josh

    Can I use this with my 2G?

  • Rajat

    no Josh, sadly Apple hasn’t released any firmware for iPhone 2G. even the iPhone 3G doesn’t have all the features.

  • Pingback: Update about iOS 4.2.1 Unlock for iPhone | Apps on Apple()

  • Daniel


    I installed 4.2.1 and performed the JB as specified.
    I then installed appsync for 4.2

    I was able to see on the iphone all apps that i purchased through the app store.

    I then proceeded to install apptbackup from cydia, in order to restore my cydia apps, ran the restore, at some point received a warning message on the iphone that it was low on memory, but it finally completed and all cydia apps appeared on the iphone.

    Then things began going strange:
    1. I received an 1034 error (not sure now) in itunes in my pc and was no longer able to sync.
    2. After reinstalling 4.2.1, performing jb etc, most of the apps purchased via the appstore do not sync to the iphone (but they do appear in itunes).
    3. I redownloaded all of the purchased apps and resynced – they still don’t appear on the iphone…
    4. If i redownload purchased apps from my iphone appstore app – they ARE installed and do work.

    Any ideas?


    • Butthead

      Hi Daniel

      Im having the same issue you described about syncing, itunes is not intalling any app to my iphone 4.2.1, appsync 4.2, itunes 10.1

      Have you had any luck yet?
      Best regards

  • zexthatico

    here’s something i always wanted to know:

    i am currently using a spirit jailbroken 3g with a lot of unofficial apps and their data.

    if i upgrade to iOS 4.2 via redsnow, do i lose all those apps and its data?

    if so, i want to know, just to download the files with ssh and keep them somewhere else… safe.

    • You’re right. Once you upgrade to iOS 4.2, you’ll lose all the cydia apps. However, you can use AptBackup or PkgBackup to backup your cydia apps first. Later, you can restore them after the upgrade.

      You can also check out this post about how you can backup the apps manually.

      • zexthatico

        yeah, i do have installed aptbackup so i guess i’ll just copy the files like videos and stuff into my pc and install all the apps after upgrading 😉

        wish there was a way to backup apps like itunes does.

        thanks simon

        • DaCeige

          Ok i have a follow on question..

          Currently i am using i4 with 4.1 JB. I only have a few cydia apps installed so not to worried about them. sBsettings mostly used and folder one and firewall. So i will back these up following your above post.

          I also have many apps installed using installous which currently sync with itunes and i also have a number of apps i have bought if i really like them.
          If i upgrade to 4.2 do the apps obtained using installous stop working or disappear and after i JB (tethered for now) will they come back (itunes sync) or do they need installing again. is there a good process to saving your apps and then upgrading and JB and making sure phone is back to how it was before upgrade

          I think based on replies to this will be a big factor about wether i upgrade or not

          Cheers 🙂


  • Nasa23

    Hello, I have upgraded my iPad to 4.2.1 and used redsn0w to jailbreak it. I have followed all the procedures indicated for jailbreaking and now I’m stuck with Apple Logo. Even when I used just boot tethered now.

    Any comment will be appreciated,


    • IphoneUnlock

      Did you get any solution for this issue ? Am getting the same issue.

  • Pingback: How To Unlock iOS 4.2.1 for iPhone 3G/3GS using Redsn0w and Ultrasn0w | Apps on Apple()

  • Pingback: Lowest Prices on iPhone Stuff » Post Topic » How To Unlock iOS 4.2.1 for iPhone 3G/3GS using Redsn0w and Ultrasn0w()

  • Teddy

    Hi Simon,

    any update on the 4.2.1 tethered jailbreak for the Ipad ? its getting pretty irritating not beingable to reboot 🙁 Anything on the horizon?

  • Alex

    I have update my iphone 3GS on Wednesday and also done the jailbreak having ticked both Install Cydia and Just boot tethered right now. My phone and apps worked great up until I decided to restart my device.
    Now am stuck at the Apple Logo. Any ideas????? please???
    And can someone explain to me what does “Just tethered boot right now” means?

  • Joikaduy

    Hi Simon Please tell me how to fix error 1015 i try to download the one from your site but it not working.

  • Jacky

    Hi simon,

    I jailbroke my iPhone 3GS by using redsnow_win 0.9.6b5
    And use IPSW 4.2.1_8C148a. After jailbreak I can see Cydia
    But I can’t open it and my safari can’t browse also. Others apps
    Ok, why? My call and data usage normal. Anything goes wrong?

    • Alex

      that is the problem I has as well until my phone got stuck in the apple logo. I managed to restore it but did not attempt to jailbreak.

      • azam

        alex…i think u correct, i have same problem with that..better restore back iphone n wait new jailbreak version.. 🙂

  • Marcella

    hai Simon,
    I have upgraded my iPhone 3G to 4.2.1 and used redsn0w to jailbreak it. and now I’m stuck with Apple Logo. I can’t do anything to my iPhone. Help me,please! thanks a lot..

    • Just try to use redsn0w to jailbreak again and make sure you choose the correct firmware. Let me know if it’s okay after retry.

      • azam

        firmware mean???

  • kenneth

    hey simon i just jailbreak ipod touch 4g and installed cydia. after installing installous and download some cracked apps. i cant find where my downloaded apps stored. any some idea?


  • Ashish

    Hi Simon,

    I upgraded my iphone 3gs to 4.2.1 from 4.0. It upgraded well and then I tried to jailbreak it using “Redsn0w 0.9.6b4”. I got white color cydia on my screen but it seems corrupted one because as I click it, it crashes down. In order to retry the jailbreak, I had to restore the phone to factory default with latest OS v 4.2.1.
    Now unfortunately I am stuck to the screen where it is asking for valid SIM card. I don’t have any ATT SIM card, what to do know? How can I successfully run my iphone back with my old conncection?
    Please help…


  • Look people I am getting a big problem, I have an ipod touch 2G 8gb and I updated its software to 4.2.1 and did the jailbreak everything went ok, very smooth and cool, but after a few days – went to my pc (windows xp) and I wanted to manage some songs the ipod had since I updated with itunes they didn’t erase, and I clicked the manually manage songs box cause I couldn’t manage my songs, and ithe thing is that my computer now doesn’t recognize my ipod it is very irritating I don’t know what to do and I’m going nuts. My pc recognizes the ipod and appears only the fotos I got in it as it appears as a camera when I open my pc, but in itunes it doesn’t show up !! I can’t do anything, I can’t see my music, videos, nothing appears on the devices in itunes, when I connect it it just charges the ipod and shows the pics opening it from my pc but nothing else….!! Please someone help me, I did the services thing nothing happenned, the usb is fine, latest itunes, it seems as if it is the ipod, I even connect another 2g 8gb likE mine running a 4.0 jailbreak sotware and its perfect, but I can’t run mine, I’ve tried everything posible, please give me a hand here, thanks….

  • Ashish

    Hi Guys,
    Any news on when are we getting windows compatible issue free untethered jailbreak tool for iphone 3GS with 4.2.1 version?

  • Ashish

    Hey Guys,

    This site appears little old and dead.
    check this out “http://www.jailbreakmatrix.com/”…it has latest updates along with active replier.

  • Hey Simon, for hw long can wait for unlock solutions to 4.2.1 (15.14…)baseband?