Let’s say you recently updated your iPhone to iOS 4.2.1 and for various possible reasons, you are already regretting this move. It is possible to downgrade your iPhone 4.2.1 to a previous iOS, but for this, you need to have your SHSH blobs on file for the iOS you want to downgrade to.

To be completely clear, if you don’t have your SHSH blobs on file for the iOS you want to downgrade to, you will not be able to downgrade. There is no way around that. This being said, here is how to downgrade iPhone iOS 4.2.1 to  4.1, 4.0.2, 4.0.1, or 4.0…

During the downgrade process, your iPhone contacts Apple’s servers to sign the firmware and make sure it can be downgraded. When a new firmware comes out, Apple signs the previous one for a few more days then stops, so technically, you can’t downgrade any longer.

The trick is to make your iPhone believe it is talking to Apple’s servers, while in fact it is talking to Saurik’s servers where your SHSH blobs are saved. That’s exactly what we’re going to do.

Downgrade iPhone 4.2.1 to 4.x

Step 1 for Windows: Make sure you are logged in with administrator privileges. Navigate to C:/Windows/System32/drivers/etc and open the filed name “hosts” with NotePad. Add the following at the very bottom of the file: 74.208.10.249    gs.apple.com

Save the file in the same directory.

Step 1 for Mac: In Finder, go to Go > Go To Folder, and enter /etc. Search for the “hosts” file and right click on it to open with TextEdit. Add the following at the very bottom of the file: 74.208.10.249    gs.apple.com

Click Save As to save the edited file on your desktop. Name the file “hosts”, and make sure to uncheck the box that says “if no extension is provided, use .txt”. Now drag and drop this edited file to /etc.

Step 2: Download the firmware you want to downgrade to from our downloads section.

Step 3: Put your iPhone in DFU mode. Launch iTunes and plug your iPhone in. Press and hold the home and and sleep button together for 10 seconds. After exactly 10 seconds, release the sleep button while still holding the home button. Keep holding the home button until iTunes tells you it has found an iPhone in recovery mode.

Step 4: Now hold the Option key (Mac only) or Shift key (Windows only) while clicking the Restore button in iTunes. A dialog box will pop up and you’ll be able to choose the firmware you want to downgrade to, downloaded in step 2.

Step 5: Your iPhone might throw some errors (ie. error 1004 or 1015). That’s ok. It’s normal so don’t freak out and just click “ok”.

Step 6: Your iPhone should now be stuck in recovery mode, showing the “connect to iTunes” logo. To get out of this, simply download and install TinyUmbrella, launch it, then click on”Exit Recovery”.

That’s it. You should now have successfully downgraded your iPhone.

  • veeeeeeeeee

    Guys,
    I have an iPhone 3G
    Baseband 6.15.00,
    I want to downgrade my OS from 4.2.1 to 3.1.3 (4.2.1 is way to laggy).

    1)Is it possible to use this method to downgrade from 4.2.1 to 3.1.3?
    2)After I downgrade to 3.1.3, can I still jailbreak and unlock it(which redsnow should I use)?
    3)Are the steps the same to downgrade from 4.2.1(bb 6.15.00) to 3.1.3 as it is shown on this website?
    4)If I downgrade to 3.1.3, can I still upgrade to 4.2.1 later?
    Thank you so much!

    • chris schulyz

      if i were you make it easier on yourself go to 4.0.1 they still have all the good stuff and it isnt laggy and if you still want 3.1.3 and want to jailbreak dont use redsn0w instead go to jailbreakme.com on YOUR IPHONE and slide to jailbreak it takes about 3 minutes and works great

      • Marc

        Hello. what if i have 4.2.1. with 05.15.04? r there any options to downgrade to v4.0.1 – Modem FW 01.59.00??? thx

  • custard_cream

    I’m sorry to intrude but I want to jailbreak my iPhone, but my niece locked it, not knowing the password. I unlocked it by restoring it, only to realize that my iPhone 3g had been updated to iOS 4.2.1. I did what you told me, but it’s only saying “cannot connect (link for host file displayed) make sure path and file name is correct”. Is there a reason for this? I’m using an acer laptop by the way, and I attempted to use both mac and Windows way. I’m going to go try it on my destop now.

  • custard_cream

    O.O It works on my desktop surprisingly. I have another question, if I change the host file today and then do the rest of the downgrade tomorrow (computer problems) will it affect me?

  • janjoowa

    sorry for bad english halp me please.
    i have iphone 3gs ans hanged with itunes logo.i try for dwongrade. fixed host file new itunes with diffrent computer.exit recovry mode with tinyumralla.still on itune logo.error3419 and1206 somthing like that error come still.halp me please on this .

  • janjoowa

    Hallo evrybody have any Genius person halp me please
    i have iphone 3gs ans hanged with itunes logo.i try for dwongrade. fixed host file new itunes with diffrent computer.exit recovry mode with tinyumralla.still on itune logo.error3419 and1206 somthing like that error come still.halp me please on this

    • RodmanIsASadPanda

      Use iREB from ih8snow.com and then restore in iTunes, that always works for me

  • Libby

    I am not able to save the host file.someone please email me at libbytullier@yahoo.com

  • Anders

    I have one question.. I have an iPhone 4 whit iOS 4,2,1. I have downloaded 4,01 and when i´m trying to restore whit that firmware i don´t get up any files that I can click on.. Sorry for bad English
    Shall I rename a file so it has the ending “ipsw” or what sould I do?

    Greatful for quick anser!

    • Jo

      Are you holding shift when you press the restore?

  • BlackGuy

    I have an iPhone 3G with iOS 4.2.1 and I have been unable to get network (always get no service or single bar). I read that the solution is to restore my firmware to 3.0. Is that the only solution? If it is, how do I do that?

    • RodmanIsASadPanda

      If you aren’t on AT&T you have to get an unlock, but if you are or already have an unlock just restore, you don’t have to restore back to 3.0, although if you can its reccomended

  • Mathieu Segbe

    Hello, i have tryed this way on my iphone 3gs iOS 4.2.1 for downgrading to 4.1 its passed .
    Thanks u very much Mr Sebastien for y’r help.I hope that it’ll easy on iphone 4, have a nice day bro!!!!

  • ItsmyI

    I was jb. I did it to my iPod and enjoyed it till one day when I had to restore it. I had no idea they were gonna update the os on me. Unfortunately, I was one of the ones that was ignorant to the fact that needed to save something somewhere, my question is, am I stuck waiting for a new jb?

    • ItsmyI

      Great, guess I was one of the lucky ones, my shsh’s were saved, I successfully downgraded. If u wanna do it too. Download tinyumbrella, use it t c if your shsh is saved. There is alot of good info on the web, but there is also alot of bad. Do your research!

  • Thiago Margem

    i have a ipod touch 4 gen JB 4.2.1 without shsh on 4.1 and i want to downgrade to 4.1 that works for me?

    • messers

      RTFM. … NO SHSH, no downgrade.

  • Paco!!

    how long does it take for itunes to verify the software update?!?!

  • LeRoy

    My itunes has been trying to verify the software udate for about 4 hours. Help please!

    • ItsmyI

      Did u download tinyumbrella, do u have the TSS server on it running, did u add that line in the file of iTunes?

  • alaa

    what about backup file ? will u be able to restore file which have been backed up on newer ios to older one>>>
    for me i tried and didnt work >>> any one can help plz

  • gregzki

    hello there

    i have iphone 4 non jailbreak with 4.2.1 version is it possible to downgrade to 4.0

  • i have downgraded from 4.2.1 to 4.1 using the method here.

    everything worked fine until I exited the recovery mode using TinyUmbrella. Now apparently I need to activate my phone and I dont have a valid SIM…anything I can do?

    thanks in advance

  • Eva

    Hi, I Have a big problem, when I Opened the Tiny Umbrella program give the message do you need to kill inetinfo.exe this is normal? I need proceed instance or i cant?

    Eva

  • BlueGirl

    This didn’t work for me. I was wondering if maybe it was because I have the latest update of OS.
    If you have any advice I’d love it.

  • Karim

    My phone is locked after downgrading from 4.2.1 to 4.1! iTunes say my SIM card is not supported, while it was working perfectly before! Please HELP!

  • heey
    i have a question!
    my iphone 3G has a update from 4.2.1 and i want to downgrade it because i wanna jailbreak my iphone with http://www.jailbreakme.com/ . but if i go to that site it says that i need to downgrade my iphone can you guys help me please.

    • read the instruction above, if you don’t have an SHSH blob saved, it is impossible.

  • raja

    i have iphone 4 sale 16gb doesnt work in uk will work world wide… brand new 16gb.. i think its unlocked..

    anyone interested let me know.. raja_faran786@hotmail.co.uk

  • David

    Im trying the downgrade but when i click Shift restore it will not open the firmware restore, can anyone help

    • ItsmyI

      All I can offer is my last comm up there, did u download tinyumbrella? Is it on and running(TSS server)? Did u modify the iTunes file? Hope that helps you. Also, do you have saved shsh blobs? That’s it.

  • David

    im a newby but i downloaded the firmware and extracted all but will not open. actually i want to jailbreak and unlock it. is it possible to that with fimware 4.2.1

  • DunknoStyll

    I have an Iphone 3g 4.2.1 downgrading to 4.0.1, and i followed al the steps to this and after the iphone extracts from opening the version i want, it says unknown error so i click ok, but then nothing else happens. am i supposed to just cliick restore again? what am i supposed to do???

  • Renato

    Will downgrading the ios also downgrade the baseband? The reason why im asking is cause i wanted to unlock my phone (iphone 4 4.2.1 baseband 3.10.01). I know i can unlock the 4.1 but i’m not sure it can be done if the baseband is still the 3.10.01…
    Desperatly waiting for an answer…

  • ManaloX

    09/02/2011 01:58:21.791 You have saved your iPhone3G 4.0 (*****) SHSH locally and the request was sent to CYDIA. This means that CYDIA DOES have your SHSH. Do NOT bug semaphore about the Cydia home page showing this version.

    09/02/2011 01:58:28.483 You have saved your iPhone3G 4.1 (*****) SHSH locally and the request was sent to CYDIA. This means that CYDIA DOES have your SHSH. Do NOT bug semaphore about the Cydia home page showing this version.

    I used the tinyumbrella and clicked on the save SHSH, this are the few things that came out… does this mean that i have a save 4.1 and 4.0 SHSH on CYDIA?

    Thanks for the reply… i need to verify this before i continue further…

  • vmzi

    Great tutorial. Thanks a Ton! was able to downgrade my 4.2.1 iphone 3g to 3.1.3 successfully following this tutorial.

  • Dean Hassan

    I can’t get out of the recovery mode, I tried everything!!!!! I have an Ipod Touch 2g with 4.2.1 trying to downgrade to 4.0. HELP!!!!!