[CM13]Install Android 6.0 Marshmallow on AT&T Galaxy S3 SGH-I747


After Galaxy S3 GT-I9300 in this guide you would be able to install Android 6.0 Marshmallow on your AT&T Galaxy S3 SGH-I747 via Unofficial CyanogenMod 13 ROM. Galaxy S3 is an old devices but still it exists in the heart of developers, that’s the reason now Galaxy S3 with the AT&T variants is going to taste the Marshmallow sweetness via Unofficial build of CM13. Previously we have posted the same tutorials on other devices and in this guide we are going to follow the same, just go ahead and follow the sequence of steps as mentioned below.

Note: The Android 6.0 Marshmallow ROM for AT&T Galaxy S3 I747 is currently in the testing stages and you may experience some bugs but most of the features are seems to be working fine.

How to install Android 6.0 Marshmallow CM13 ROM on AT&T Galaxy S3 I747

Before you Begin:

Disclaimer: This tutorial includes multiple operations including Custom Rom, custom recovery etc. Follow the guide on your own risk, we are not responsible if you brick or damage your device however the chances of bricking a device are rare but you have to pay full attention on the complete guide to avoid any issues and difficulties while performing any of the above mentioned operation.


  • Please ensure your phone battery should be charged at minimum 80%
  • Download Samsung USB drivers
  • Your device should have a working TWRP or CWM recovery installed in your device.

Necessary downloads:

Process to install Android 6.0 Marshmallow on AT&T Galaxy S3 I747

Connect your device to your PC and copy the both ROM and google apps zip files onto your device storage.

Turn of your device and boot into TWRP custom Recovery menu by the hardware keys combination or using any third party app (Mostly found in Play store).

Once your device enters into TWRP recovery, create a Nandroid backup of your device or follow our guide to create a Nandroid backup (this will create a backup of your complete device including current firmware) if something goes wrong you can restore your previous firmware.

Once the Nandroid process completes, tap on “Wipe” and then swipe the slider from left to right to begin the wipe process (This will reset your device to factory)

Now it’s the time to flash the Marshmallow firmware on your device. Choose install and navigate to the folder in which you have copied the cm-13-20151104-UNOFFICIAL-d2att.zip file

Swipe across the slider to confirm install, wait for a few minutes till the file is completely installed in your device.

Once done with the above step, now apply the same process with the installation of gapps.

Wait for the installation process to complete.

Once the installation process is completed, reboot your device.

If your device is taking longer then 7-10 minutes then follow this guide to to fix this issue

That’s it! You have successfully installed Android 6.0 Marshmallow on your AT&T Galaxy S3 SGH-I747 via Unofficial CyanogenMod 13. If you have any query feel free to contact us by posting your queries in the below provided comment section. Follow us on Facebook/Twitter/Google+ for future update.

A Software Engineer who loves to hang around latest gadgets and writes his own experiences to get the best possible and accurate information.
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