How to Jailbreak iOS 4.2.1 with Greenpois0n on Windows


The Chronic Dev Team released their untethered jailbreak, Greenpois0n for iOS 4.2.1. This jailbreak is now available for Mac and Windows users.

If you’re on Windows, you can follow this brief overview on how to jailbreak with Greenpois0n. As always, do your research, and then proceed at your own risk.

This guide will jailbreak your iPhone 3GS and iPhone 4 on iOS 4.2.1 on Windows (click here for the Mac tutorial).

– sync your iPhone in the latest version of iTunes.
– if you NEED your iPhone unlocked, do not update to iOS 4.2.1 via iTunes (you should know this by now).

1. Download Greenpois0n for Windows here to your desktop and launch greenpois0n.exe

2. Turn off your iPhone. In Greenpois0n, click “Prepare to Jailbreak (DFU)”. Now you will get instructions on how to enter DFU mode.

3. You’ll be asked to…
– press and hold the Sleep button (2 seconds)
– continue holding sleep; press and hold Home (10 seconds)
– release sleep button; continue holding Home (15 seconds)

4. Once you’ve entered DFU mode, click “Jailbreak”. Greenpois0n will now work its magic and jailbreak your iPhone 3GS/4.

5. Once finished, click QUIT in Greenpois0n. Some text will scroll on your iPhone’s screen and will restart.

6. After the restart, you’ll notice the Loader app on your homescreen. Launch it.

7. Select Cydia, and then tap Install. Once finished, hit Options and tap Remove

8. Restart iPhone, load Cydia and install updates. Done!

Let me know how this brief tutorial works for you. If it fails the first time, you probably did not enter DFU mode correctly. Try again.


  • Great Post Bro, Thanks alot. Love from Bahrain! 🙂

  • You’re welcome!

  • Anonymous

    So if you have 4.2.1 already installed,Can you unlock it or no using ultrasnow?this is an iphone4

  • dr_slurpee

    Does anyone know if iPhone 3G is supported?

  • i never tried this but hoping it would be way better that Redsn0w

  • Cake

    If you are on 4.2.1 already you can just ru greenpoison .There is currently no unlock available.

  • Rpsfyn

    Is it worth waiting for iOS 4.3 ? or should I just jailbreak it for 4.2.1?

  • AnonymousGuy

    This is a common stupid question everyone keeps asking. For one, you can’t Jailbreak 4.3 yet. Also, other than the built-in hotspot feature (which you can alredy get via MyFi on Cydia), no it’s not worth “waiting for” and upgrading to. Jailbreak 4.2.1 NOW, and don’t upgrade to 4.3 until a Jailbreak is released for it in April or so. ‘Nuff said.

  • Anonymous

    3G was supported many moons ago.
    It is usually the first iDevice to be jailbroken when a new iOS is released.
    Dont use Greenpoison though. Try Redsnow

  • Darrinathumber

    anyone else having trouble unzipping? I keep getting message it is a virus

  • Accordxtc

    DO NOT USE GREENPOIS0N, twice now trying to jailbreak its bricked the iphone. This update is not fully working yet with iPhone 4. Bewarded, I’ve been doing this since the 3G day’s so I’m not new to this.

  • AccordXTC

    Yep I did as well and turned off my AV software and then this wonderful GreenCRAP bricked my phone twice. Its awesome now I’ve lost my jailbreak. Dont run it

  • SF

    Everything was very smooth. Thank you so much iphoneincanada and dev-team!

  • Ex

    It’s working fine.

    I’ve done two iPhone 4 and a 3GS.

  • Ex

    It’s working fine.

    I’ve done two iPhone 4 and a 3GS.

  • Jeangreg

    Yep two iphone 4 done no problems!

  • Suspended Mirror

    So I bought my iPhone outright and unlocked and I noticed that the warning says do not jb if you want to unlock your phone. I don’t want to loose my unlocked state will jbing affect that

  • Kamal Muzahar

    That doesn’t apply to you. Go on, just jailbreak it, urs will still remain unlocked

  • Suspended Mirror

    Err I should be more clear and say that my iPhone is a factory unlocked iPhone

  • Ex

    If you bought your iPhone unlocked, then you’re safe. It will always be unlocked

  • AnonymousGuy

    You’re obviously doing something wrong. Works fine on my iPhone 4, and thousands of others have had success. It’s only the idiots that don’t follow directions properly that are having problems.

  • Anonymous

    Yep, you’ll be fine. There is no way to lock a factory unlocked phone just by jailbreaking.

  • Subzero

    Does it show skull apple for everyone else too?

  • Davebissoon

    I jailbroke my phone to iOS 4.1. Do I have back up my apps & other programs from Cydia before jailbreaking to iOS 4.2.1
    Please help, jailbreak rookie.

  • Ex


  • did mine before the update, on a mac. it had a few issues, but after a couple of tries worked ok. If you think you “bricked” the phone, then you obviously haven’t been doing this as long as you said, or don’t know what you are doing. worse case, you update back to 4.1 or 4.2. or use Redsn0w. In fact i had issues with the loader as well, and just used redsn0w to put on cydia. Its really hard to actually “brick” the phone, but then again i am not sure what your definition of brick is.

  • Anyone else stuck in safe mode after this? I am and I can’t seem to get out of it. Ideas?

  • dr_slurpee

    Doesn’t redsnow require tether?

  • Ex

    Safe mode on your computer or iDevice?

  • On my iPhone.

  • Oh ya; and I never got the loader app on my homescreen either, but I was already jailbroken with redsn0w and had to jailbreak over my greenpois0n to get my phone to boot. It was stuck in the “connect to itunes” screen.

  • Ex

    If you’re JB with Redsnow, just run greenpoison. Loader won’t be there cause you already have Cydia

  • I ran greenpois0n and it stuck my phone on the screen with the USB cable and the iTunes logo. I had to JB again with redsn)w just to get my phone to work. Now the springboard is stuck in safe mode and won’t fix. Cydia won’t update either.

  • Subzero

    That’s a bit creepy but mostly lame shameless plug.

  • Anonymous

    For 3G, or an old-bootrom ipt2g or iPhone 3GS, redsn0w is untethered. It was only tethered for the newer-bootrom iPhones/iPods (later 3GS/iPhone 4).

  • greynotegroup

    On Cydia Changes Refresh, I Get:

    Updating Database
    Downloading Release
    Error: POSIX : Operation Time…
    Downloading Release.gpg
    Downloading Release

    then it Reloads Data and its done.

    Is the POSIX: Operation Timed out an issue I should be concerned with?

  • Pturvz

    First time jailbreaking, and it seems to have worked very well. It failed the first time, so I reset my phone, tried again and it worked. I apparently just didn’t enter DFU mode correctly.

    Thanks Gary!

  • greynotegroup

    works fine now…

    Maybe an overloaded server over weekend.
    Great Jailbreak. Simple to use, no problems.

  • Zeus_369

    Worked like a charm! Thanks for the super easy walkthrough!

  • Indianajones

    I need help… when the screen scrolls… The last line says “panic: we are hanging here…” what does that mean? Please help

  • Ex

    And the screen just sits there?

  • Indianajones

    I get the message… panic: we are hanging here. What does that mean?

  • Ex

    Probably need to redo the process.

    Hard reset and redo.

  • Indianjones

    H… the screen this sits there. I did a hard reset and tried it again and it froze in the same place with the same message.

  • riffic

    This works great. Never did a jail break before. Screwed up the first time and it just sat there, so I did it again and it worked like a charm.
    greenposiOn works great.
    Only down side is, I find Cydia does not have much there of any real use… just a few things.

  • Nice work!

    Download SBSettings, Five Icon Dock, biteSMS, MyWi, and My3G to start.

  • Anonymous

    Having a weird issue with my Safari crashing. It started about an hour ago. Strange since I’ve been running the JB with no issues since it came out. Anyone else?

  • Zilly

    Did you get it working??!

  • Indianajones

    Nope.. not working yet! Same panic message

  • Wolfhawk

    I have tried about 10 times, with no success. I must be an idiot as soooo many people seem to make this sound easy. I follow the prompts but the loader just sits there, then the green progress bar goes quickly across, finally I get “Jailbreak Failed :(”

  • Ex

    Are you on firmware 4.2.1 right now?

    Is your device OFF and plugged in before starting the process?

  • Kim

    I have iOS 4.1 with BB 1.59. I want to upgrade to 4.2.1 and jailbrake and still keep my BB to unlock. Do I need to do anything special or just go ahead and upgrade and do the jb. Does the new version of iOS comes with a new BB version as well? Been out of the scene for a while and trying to catchup with all the current stuff. thanks

  • Rustybarnacle

    I’m wondering why this isn’t news on the ipad sister site here. According to this article is not available for the ipad but several other places say it is.

  • S3c0nd4ry

    You are obviously doing something wrong, lol.

    your like the people that come into my phone store, who don’t know how to work their phone properly and call all kinds of stuff “broken” or “defect” because you haven’t taken enough time to read how to do it properly.


  • Asdf
  • 7turn1

    Those are my favorite as well but I like infinidock instead of five icon dock. MyWi is useful too.

  • 7turn1

    Sorry I just seen MyWi there. Lol

  • Re_care

    can i jailbreak my iphone 4 (4.2.1) and then unlock?
    I want to unlock my iphone 4. Please help.

  • Use tinyumbrella first to preserve baseband.

  • iamlynda

    Oh My GAWD!! total newbi here. have wanted to jailbreak for a long time but was terrified. I just did it via Greenpois0n-THANKS Gary the fab dev team!!! it took several trys but finally got it. couple tricks to note should be you must hold the home key for the full 15 secs – the timer disappears after about 5 – keep counting to 15. Then when all that goobooly-gock text scrolls down the screen – be patient – it takes several minutes to complete. Do not unplug! I did it and had to start all over again. Also my *bleepin* auto play kept powering my phone back on- finally when the auto play turned it on I just left it connected and powered down. now Iam happily scouring Cydia for all those recommended apps!! YAY Freedom!!

  • Way to go!! 🙂

  • Eric

    It’s more stable on he iPhone 4. I’ve jailbroken 2 iPhone 4s and 3 iPhone 2s with it. Worked every time. For it to brick your phones twice, you must have horrible luck, or, more likely, you’re doing something wrong.

  • James

    my itouch screen goes white after the jailbreak… WHY?

  • Carlos

    i click the sleep and home button right and do everything else right. Then it gets stuck on the text page and doesn’t do nothing it stays like at half page what should i do?

  • A Toma94

    hey guys, i don’t know if this is right to say this, but since im Iphone 3gs 4.2.1 newbie, after jailbreaking it, my goal was to unlock it(i installed UltraSnow 1.2 via cydia) and after wondering why its not unlocking, i later researched about unlocking it it and found it(redsnow) *facepalm* However i restore in the iphone settings, and all of the sudden the boot goes on and then into greenpoison, and froze and the screen went black, is there anyway(s) to restore to factory default?

    sorry for my english

  • Ex

    Restore to default with “recovery” mode or “DFU” mode.

  • Jabbawockee_7

    my phone doesnt restart at the end of the jailbreak, it just shows the connect to itunes screen. what do i do??

  • Khansen55555

    i clicked jail break and held in – press and hold the Sleep button (2 seconds)- continue holding sleep; press and hold Home (10 seconds)- release sleep button; continue holding Home (15 seconds)
     it said to turn it on and then connest it and it wont turn on .. battery was fully charged

  • sexybitch666

    did everything and clicked quit  and white text went on until it is like1/4 or 1/3…. somewhere in between and then it doesnt restart

  • Sobased28

    ok after click jailbreak its starts but then once it gets to the words on my screen it stops there and freezes what should i do????

  • JakeNBake

    Hey im having same problem, and yes its turned off before i start the process