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How To Untethered Jailbreak iPhone 4 or 3GS on iOS 4.2.1 for Windows User

Greenpois0n logoFinally the Windows users can now enjoy the untethered jailbreaking for your iPhone, iPod touch or iPad. As you may already know Greenpois0n for Windows has been released.

If you haven’t heard of Greenpois0n, it is the first stable jailbreak tool that supports untethered jailbreak on all devices running iOS 4.2.1. Developed by the Chronic Dev team, the tool doesn’t require you to have the SHSH blobs. You can simply jailbreak your device running iOS 4.2.1 out of the box.

I have tried to jailbreak my iPhone 4 using Greenpois0n. Despite there are a few hiccups, overall speaking, the jailbreak process is quite smooth. Here I come up a step-by-step jailbreak guide to walk you through the process using Greenpois0n. If you’re using iPhone 3GS or iPhone 4 and would like to jailbreak your device on iOS 4.2.1, you can simply follow the procedures and achieve the jailbreaking.

Before we dive into the jailbreak process, please read through the notes very carefully:

  • This guide is for Windows user. If you’re using Mac, please check out the untethered jailbreak guide for Mac users.
  • Greenpois0n is a jailbreak solution that allows you to open up your device to install 3rd-party applications. It’s not a software-unlock solution. So if you are currently relying on Ultrasn0w to unlock your iPhone, please DO NOT upgrade your iPhone to iOS 4.2.1 directly. Otherwise you’ll lose the unlock and your iPhone will not be able to make call.
  • Greenpois0n does not come with hacktivation. That means you have to activate your iPhone before using the jailbreak tool.
  • Greenpois0n works only on iOS 4.1 and 4.2.1. However this guide is written based on the jailbreaking of iOS 4.2.1. We have not tested it on iOS 4.1.
  • Make sure you’re using iTunes 10.1 or up.
  • If you have used Redsn0w to jailbreak (untethered) your iPhone, I suggest you to restore it to iOS 4.2.1 via iTunes before using Greenpois0n.

Note: If you have any questions after reading the note, feel free to leave us comment before kicking off your jailbreak journey.

Okay, let’s get started.

Preparation for the Jailbreak

1. Download Greenpois0n RC5_2 from or mirror site.

Note: I suggest you to download the tool from the mirror site. The official site is extremely busy and not very stable for now.

2. Extract the and you’ll have the “Greenpois0n” application.

Kick-off the Jailbreak Process

3. Connect your iPhone to computer via USB cable and power it off.

4. Launch the Greenpois0n application.

5. Click the “Prepare to Jailbreak (DFU)” button to kick off the jailbreak process. You can simply follow the on-screen instructions to put your iPhone into DFU mode. Keep holding the home button till the end of the jailbreak process.

Note: If you fail for the first time, power off your iPhone and goes through the process again. It won’t hurt.

6. As you successfully put the device into DFU mode, Greenpois0n will automatically jailbreak your device. On your iPhone, you’ll see the verbal messages in command mode. That’s normal. Just wait until Greenpois0n tells you the process completes.

Installing Cydia

7. After jailbreaking, your iPhone will be automatically booted up. You should find a new icon called “Loader”. Simply tap on the icon and launch the app.

greenpois0n loader app

8. Once launched, tap on the “Cydia” button to install cydia. This will initiate the download process. Just wait for it to complete and you’ll have cydia installed on your iPhone.

greenpois0n loader app cydiagreenpois0n loader app cydia download

Note: If you found the cydia button missing after launching Loader app, just quit it and try again.

9. After successfully installing cydia, you can tap the “Option” button and remove the Loader app.

About Simon Ng

Founder, developer and chief blogger of

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63 Responses to How To Untethered Jailbreak iPhone 4 or 3GS on iOS 4.2.1 for Windows User

  1. melanie February 7, 2011 at 6:44 am #

    I have an iphone 4 with firmware 4.0 and already jailbroken using “JailBreakMe” but I want to jailbreak with the greenpois0n new jailbreak so I can update to firmware 4.2.1. So what steps do I need to take before I can go with this new jailbreak?

    • Simon Ng February 7, 2011 at 12:43 pm #


      Do you need to rely on ultrasn0w for unlock? Or you’re already using a factory-unlocked iPhone 4?

      • Melona February 7, 2011 at 2:04 pm #

        My phone isn’t unlocked..I’m with AT&T so it’s only jailbroken using Jailbreakme. I just want to update my firmware to 4.2.1. So if I use this new jailbreak do I need to first update my firmware to the 4.2.1 then go ahead with new jailbreak?

        • Simon Ng February 7, 2011 at 2:40 pm #

          As you’re using AT&T, simply upgrade to iOS 4.2.1 via iTunes. Activate it and then follow the procedures in this guide to jailbreak your iPhone with Greenpois0n.

  2. chikanoz February 7, 2011 at 1:24 pm #

    hi simon, one question..

    before i perform the gp program, do i need to download ios4.1 and load into my iphone?

    *im using ifon 3gs with ios4.01 [previously jailbreak by jailbreakme]

    • Simon Ng February 7, 2011 at 2:42 pm #

      Yes, you’ll need to upgrade to 4.1 or 4.2.1 before jailbreaking. I assume you do not need to use ultrasn0w for the unlock.

  3. david February 7, 2011 at 4:19 pm #

    Hi Simon,
    I success to DFU mode,

    but after I click on the JailBreak Button (For Windows) then it start jailbreak but after awhile it say jailbreak fail……. tried for more than 10 times…… pls advice,

    my device
    Iphone 4 = 4.2.1
    modem firmware = 03.10.01

    • david February 7, 2011 at 8:30 pm #

      forget to inform that itune version =

      • Don February 7, 2011 at 10:04 pm #

        David, make sure you are not connected to a USB hub and even some laptops aren’t strong enough on USB to work. Plug it into the back of a desktop and then run it again.

        • David February 8, 2011 at 7:14 am #

          Hi don, I m using direct USB fr laptop but still the same prob

  4. Subbu February 7, 2011 at 8:31 pm #

    Hi Simon,
    I have my iphone 3GS (new MC model) and used Ulatrasn0W to jailbreak (4.2.1 version) and redsn0w to unlock (the one that our iphone dev-team released in last Christmas), I had to upgrade to 6.15 baseband to make this happen. Could you please advise, if I can still use this Greenpois0n to make my phone untethered? I believe, i should go thru redsn0w process to unlock after I jail broke with GreenPois0n. Please suggest.

    • M0N15H October 21, 2011 at 1:00 pm #

      Hi Subbu,
      I am in a very similar situation like yours. And please excuse me, as my knowledge & understanding about these JB, Untethered, etc.. terms are not easy for me. But, I am still expecting help from you personally, as you could understand this best.
      My Phone : iphone 3GS
      Version : 4.2.1 (8c148a)
      Model MC555LL
      Base Band / Modem Firmware : 06.15.00
      I am currently using this as Unlocked – but tethered by Redsn0w. I want to use it as Untethered, but keeping in mind that NONE of my Apps., and DATA should be affected. I have downloaded “greenpois0n RC6.1 (win)” Please reply me soon, whether loading the above file would affect my DATA & Apps in any way except making it untethered. Thanks in ADVANCE,
      — M0N15H..

  5. Steve February 7, 2011 at 11:57 pm #

    I’m iPhone 3G. I’m 6.15BB 3.1.3 OS. Please how can I update to 4.2.1 and JB with GreenPoison?


    • Dav February 8, 2011 at 5:37 pm #

      U can use iTune to upgrade to 4.2.1
      then use GreenPois0n to JB ur device

      • Steve February 8, 2011 at 8:03 pm #

        Thanks Dav,
        But I’ve already tried, iTunes wouldn’t let me upgrade to 4.2.1 I am aware I need to use custom FW. Even that I’m encoutering errors…

  6. TK February 8, 2011 at 1:09 am #

    Thanks Greenpois0n…I manage to jailbreak my Iphone4 with 4.2.1. Thanks again…

  7. lee jam February 8, 2011 at 1:17 am #

    Dear Simon, unlocking is a must for me…is there any news or any effort goin on for an unthetered unlock? Out in the vicinity soon? either wth version 4.1.2 or 4.2.1. Btw, grt blo, vry informative, keep it coming…thanks, regards

  8. SK72 February 8, 2011 at 2:42 am #

    Thanks Simon. I already had a tethered jailbroken iPhone4 running on iOS 4.2.1. My untethered jailbreak went fine without any errors. There was some scripts at the beginning which said “failed to …”, total 3-4 errors in the beginning but the jailbreak went fine. The total time to jailbreak was around 5 minutes.

    [Windows XP Pro, iPhone4 (4.2.1), iTunes]

  9. apple mate February 8, 2011 at 4:35 am #

    hi guys!
    i got an iphone 4 ios 4.0.1 factory unlocked frm U.S, and wanted to update it to 4.2.1 and then jailbreak it using the green poison,,,but worried about my baseband up gradation issues,,,please help me out!!!

  10. jacky February 8, 2011 at 8:09 pm #

    dear simon,

    may i know if my ipad OS is 4.2 version, can i jailbreak using GreenPois0n.

    Kindly advice.


    • Simon Ng February 10, 2011 at 12:17 am #

      Yes, Greenpois0n should also work for iPad.

  11. SK72 February 9, 2011 at 12:08 am #

    @Jacky..See my message above..I did an untethered jailbreak on my iPad (4.2.1) the same way I did for my iPhone4 (4.2.1)…only difference is I don’t see a Greenpois0n animated logo on the iPad when it boots up…In both the case I already had tethered jailbreak..



  12. Jim February 9, 2011 at 9:57 pm #

    Hi Simon,

    I tried to jailbreak 3GS running on 4.2.1(8c148a) Firmware 05.05.04 Tried few times it hangs after jailbreak fail and can’t on the phone. Had to restart com re-plug cable run the jailbreak and the phone can restart again can advise?

  13. duncan February 9, 2011 at 11:57 pm #

    tq so much it work on my iphone 3GS 3.1.2~

  14. ApplefreaK February 10, 2011 at 4:10 am #

    Can i really jailbreak my factory unlocked iphone 4, will it not hamper the baseband??

  15. Shane February 10, 2011 at 9:42 am #

    Hi there I have a tethered jailbreak on my 3GS new bootrom from redsnow I am wondering do I need to restore it then jailbreak on gp for it to be unthethered ?

  16. Sunny February 10, 2011 at 1:48 pm #

    I have a Iphone 3GS with 4.2.1 I need to unlock it and jailbreak it. It has been jailbroken before using redsnow which id tethered wherein I have to boot always using the computer.
    My question is If I follow the process given above will I loose the unlock??? If I want to unlock again after untethred jailbreak given above how do I do that?
    Please help
    Thank you

  17. jacky heng February 10, 2011 at 8:26 pm #

    dear simon,

    my iphone 3g with 4.2.1 totally locked after using greenpison.

    my phone can’t go to the home page, it always loading with apple logo only.

    Please help and advice.


  18. Jsrking February 12, 2011 at 11:07 pm #

    Hey Simon!

    I have a locked 3G using 4.2.1 with 05.15.04, Can I jailbreak it with this greenpoison’s guide? I saw an older post to jailbreak and unlock but I’d had to install an Ipad BB? What’s my best choice?

  19. satamoony February 13, 2011 at 1:55 am #

    after trying jail breaking an iphone 3Gs ios 4.2.1 the screen became black i tried to press the sleep button alot and long, but it doesnt work… I even tried to charge, but the iPhone didnt give any response.. Then I tried to plug on to my computer but my iPhone still dont respond.

    No apple icon, it just stays black…

    Help pls I need my phone really hard tonight !! D:

    • Salam March 31, 2011 at 8:38 pm #

      Hi satamoony,
      I have same problem and I cannot restate my iohone again . it is now shows a USB and that is .
      have you sort out the problem in your iphone ?

    • Hatim July 13, 2011 at 5:18 pm #

      Hold down the sleep and home 15sec release home and it should start. worked for me after 10 min of freaking out lol

  20. Drew February 13, 2011 at 8:35 am #

    Hey, easy question for you guys. I have already jailbroken my 4.2.1 4G with redsn0w, and I saw that its recommended her to restore my iPod before I jailbreak with Greenpois0n. Is it possible to back it up before I do so, jailbreak, and then restore all the apps I have built up over time (as well as Cydia apps), or is it not possible to get these back?

  21. Bernie February 13, 2011 at 9:25 am #

    I have a 3G and every time I run green poison it says try again. Because it’s seems it’s not finding the phone in recovery mode.

  22. Tommy February 14, 2011 at 5:34 am #

    Hi simon i have ipad and my i cant syn with my computer, but iphone are ok. Can you tell me what wrong? Thank in advance.

  23. Tasha February 16, 2011 at 9:39 am #

    Thank god they finally came out with Greenpoison for windows! Thank u! I only jailbroken my phone with redsnow and I was wanting to know how to unlock it?? Thanks Tasha

  24. Edwin February 18, 2011 at 4:28 pm #

    Hi Simon,

    I have a question and hope that you can assist me for my iphone 3GS.

    I update my iphone 3gs a few days ago, then it goes successfully. After that, I found out that there is no network anymore until today. Iphone can’t recognize my sim and it always show up the “Ïnvalid Sim”. I try to reset the network, but it still the same Invalid Sim (NO NETWORK). I couldn’t use it anymore.

    Please advice what i will gonna do for this situation.

    Best regards,


  25. Timothey February 22, 2011 at 8:43 am #

    I used your help to jail break my iPod 4, and it worked like a charm. Thank you so much. I tried other people’s instructions, and your’s were the only I could get to work for me. Thanks again :-)

  26. DJ February 25, 2011 at 12:53 am #

    Is it safe to use Greenpois0n on a factory unlocked iphone 4 4.2.1 03.10.10 for an untethered jailbreak? Would that be rc5_2 or is there a later version?

    Thanks, DJ

  27. DJ February 25, 2011 at 12:54 am #

    Is it safe to use Greenpois0n on a factory unlocked iphone 4 4.2.1 03.10.01 for an untethered jailbreak? Would that be rc5_2 or is there a later version?

    Thanks, DJ

    • Simon Ng February 25, 2011 at 1:51 am #

      Yes, it’s safe for factory unlocked iPhone. The latest version is RC6.1. Please download it from

  28. DJ March 1, 2011 at 1:26 am #

    Hi, I just completed the jailbreak of my factory unlocked Iphone 4 4.2.1 with Greenpois0n. Everything seems to have gone well. My question is I see mention everywhere of Appsync 4.2 but the highest I see in Cydia is 4.0+, are they one in the same and is that the one I should use?

    Thanks, DJ

  29. DJ March 2, 2011 at 3:25 am #

    It took a lot if searching but I found out I should use appsync 4.0+ and it is working great!


  30. Leslie March 6, 2011 at 9:53 am #

    hi simon,

  31. Leslie March 6, 2011 at 9:56 am #

    hi simon, i just wanted to know if gp will work without any problems on my iphone 3gs 4.2.1 (8C148a) on modern firmware 05.15.04?

  32. Usman Kazaure Abdullahi March 8, 2011 at 3:31 am #

    Hi Simon,
    I have 3gs with 4.0 but due sycn problem with itunes it’s upgraded to 4.2.1 and now working perfectly. I can’t see Cydia on my home screen and i tried jailbreakme it’s telling me that not possible for 4.2.1. Can i use Greenpois0n to jailbreak it without loosing my unlock?

  33. jackson March 10, 2011 at 10:36 pm #

    hi Simon,
    question, do you find that your battery drain after jb with greenpoison?

  34. AZAM March 13, 2011 at 5:22 pm #

    HYE.. i already jailbreak use greenpoison but my cydia cant work perfectly… can i jailbreak again use greenpoison dont need to restore?

  35. jessica April 2, 2011 at 3:10 pm #

    Hi i have jailbreak my iphone 4 under redsnow and i would like to untethered it can any one help.

    my ios 4.2.1, modem firmware 03.10.01

  36. lori June 9, 2011 at 11:46 pm #

    iv got ios verson 4.2.8 for iphone 4 i tried to jailbreak with greenpoison and my loader app wont open iv tired it twice already but i dont want to screw up my phone by trying again or trying a different jb software any help/advice would really helo me out!

  37. tucker September 11, 2011 at 2:17 am #

    My iphone 4 was trying to get jail broken with greenpois0n and it just shut off. It wont turn back on and it wont show the logo after holding the buttons down. Help me plz

  38. tucker scott September 11, 2011 at 2:20 am #

    it doesnt show up on itunes either

  39. Louis September 23, 2011 at 10:24 am #

    Hi Simon, do i need to update my bandwidth on my Iphone3GS running on 4.2.1, my phone is already jailbreak with redsnow and is tethered.

    I heard i can just run greenpoison overtop of this but my critical question is do i need to update my bandwidth right now it is 05.15.0!

    Thanks for your reply Simon !


  40. Louis September 23, 2011 at 10:24 am #

    Hi Simon, do i need to update my bandwidth on my Iphone3GS running on 4.2.1, my phone is already jailbreak with redsnow and is tethered.

    I heard i can just run greenpoison overtop of this but my critical question is do i need to update my bandwidth right now it is 05.15.04

    Thanks for your reply Simon !


  41. Karl October 6, 2011 at 9:30 am #

    Hey I have iTunes 10.2 will gp still work for the jailbreak?

  42. Karl October 6, 2011 at 9:35 am #

    Hey I have iTunes 10.2 will gp still work for the jailbreak?Also can’t find rc5.2 on gp site only rc6.1? will that work for the unteathered jailbreak?

  43. Shylaza November 24, 2011 at 10:46 pm #


    I have a jailbroken iphone 3GS OS 4.1 and one of my friend without knowing tried to upgrade to OS 5. and couldnt do that as it is OS 4.1 now it is stuck at the first position configure. I am not able to configure. and remain at last connect ti itunes and not able to detect.
    Please help me what to do.

  44. Nicole Andrewson March 18, 2012 at 4:08 am #

    I tried to jailbreak my iphone 4G i followed all the steps but at the end it says to connect to itunes i went to itunes and it said to restore it and i did, then i jailbroke it again but it said the same thing!!!!!!

  45. pmu July 20, 2012 at 10:35 pm #

    This information is invaluable. When can I find out more?


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