How to downgrade Galaxy S3 back to Android 4.1.2: tutorial [Update]

With all the problems that S3 owners are facing with the official Android 4.3 update from Samsung, many of you are not holding out hope for a rapid fix to your problems. Neither are we. So here's how to downgrade your Galaxy S3 back to Android 4.1.2, the last firmware update prior to the current bungle. Downgrading your OS version probably never sounded so exciting. [Update: S3 owners on the AT&T network are advised NOT to try downgrading. There have been reports of this process bricking devices.]

If your S3 is suffering at the hands of Android 4.3, you can return to 4.1.2! / © AndroidPIT

What you need

Downgrading your firmware is exactly the same as upgrading, you simply use an older firmware version than the one you currently have. So if you've found yourself stuck with an unworkable 4.3 update, follow the same process you normally would to manually install the new firmware, but instead use the firmware you started with before the OTA update. First of all make sure you have a full backup of your S3 because the flash procedure will wipe your data.
You'll need Odin v3.09 and the necessary USB drivers for your S3. Make sure you also have USB Debugging enabled in Developer Options.

Odin is very simple to use and self-explanatory. / © AndroidPIT/ © AndroidPIT/Odin

Then, you'll need the relevant firmware for your device. You can find the relevant firmware for your particular model number S3 at Sam Mobile's firmware page.

What you need to do

1. Download the appropriate firmware .zip file for your S3 (link above) and extract it on your PC. You'll see a few .tar.md5 files inside.
2. From being powered off, start your S3 in Download Mode by pressing Volume Down + Power and Home button simultaneously.
3. Open Odin and connect your S3 to your PC with a USB cable. Wait until Odin recognizes the device (a blue box appears in Odin). 
4. In Odin's Files [Download] section, navigate to the relevant tar.md5 file/s in the downloaded S3 firmware. If you only have one file in the extracted firmware it goes in PDA. if you have multiple files, just plug them into the appropriate boxes in Odin.
5. Make sure the repartition box is not checked. 
6. Click Start and wait. Once the procedure is complete your S3 will restart and you'll be back to where you started from before your update nightmare began.

You probably haven't been this happy to see Android 4.1.2 in a year. / © AndroidPIT

If your S3 doesn't reboot on its own, enter Recovery Mode by pressing Volume Up + Power + Home button simultaneously and then performing a Data Wipe/Factory Reset and wipe any cache partition. Then select Reboot System Now and you should be good to go.

[Update: 8:30 PM Berlin time 26.11.13]

S3 owners on the AT&T network have reported that attempts to downgrade to 4.1.x have resulted in a bricked device. If you are on this network, please play it safe and DO NOT attempt to downgrade, just in case. At least until you've read more and are aware of the risks involved. You can read more about these bricking cases and the current status of attempts on the following XDA Developers thread. S3 owners on any other networks would be advised to search XDA for any other bricking cases before proceeding. My thanks to AndroidPIT reader Amir Y for bringing this to my attention!
Have you been suffering from the Android 4.3 update? Has it prompted you to start flashing your own firmware?
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