AT&T Galaxy S3 Marshmallow CM13 Custom ROM Update

Samsung Galaxy S3 has now got the CaynogenMod CM13 Custom ROM to update the device to Android Marshmallow. This custom ROM has all the features of the original Android Marshmallow update. Samsung has not released its Android 6.0 Marshmallow update plans, for the device, so you can expect some delay on Marshmallow update or it may not be available at all.Sprint Samsung Galaxy S3


If you are anxious of updating your AT&T leased Samsung Galaxy S3 to Android Marshmallow, then here is an unofficial way of doing that. The CM13 ROM is unofficial but it has all the features of Android Marshmallow official update. This CaynogenMod CM13 ROM work well and it does not have any faults.

Preparing your Phone

  • Device should be fully charged up to 100%.
  • Backup all the important data to some external storage.
  • USB drivers  for device should be installed on the PC.
  • Make a Nandroid backup of the current ROM in case the new version does not work properly you can restore it.
  • Custom recovery like TWRP must be installed on the device.
  • Device should be rooted and its bootloader must be unlocked.
  • USB debugging mode should be enabled on the device. Go to Settings > Developer options > USB debugging mode.USB Debugging

Android Marshmallow CM13 on Samsung Galaxy S3

Follow the process mentioned below to install Android 6.0 custom ROM via CyanogenMod 13 on Samsung Galaxy S3 smartphone –

  1. Download the Android Marshmallow AOSP file from here.
  2. Download Android Marshmallow Gapps file from here.
  3. Transfer the Files to Device internal or external storage.
  4. Turn off the device and reboot it into Recovery mode by using appropriate hardware buttons.
  5. In recovery select Wipe option and then tick the Data, Cache, Dalvik Cache from the next page.
  6. Swipe the Swipe to wipe button at bottom of the Screen.
  7. Now return to main menu and select the Install options.
  8. Navigate to the ROM zip file and select it, then swipe the button at bottom to flash it.
    1. In the same way flash the GApps file.
  9. Return to main menu and select the Reboot option to reboot the device.

Your device will now be updated to Android Marshmallow, you can check the version of Android in Settings > About device.