Update AT&T Galaxy S3 to CM 13.0 Android 6.0.1 Marshmallow Custom ROM

Samsung Galaxy S3 is one of the old Samsung’s flagship device but these smartphones might not receive the latest Android OS updates via OTA from the company. However, thanks to the CyanogenMod team that the official CyanogenMod 13.0 Nightlies are now available for the Galaxy S3 (AT&T variants). CyanogenMod builds are popular for better performance and stability and are based on the AOSP Android 6.0.1 Marshmallow releases. Official ROMs are usually good but if you want to taste tons of extra functions and features then go ahead and follow the given guide to install CM 13.0 Marshmallow Custom ROM on Samsung Galaxy S3 (AT&T).

Update AT&T Galaxy S3 to CM 13.0 Android 6.0.1 Marshmallow Custom ROM 1


This CM13 Android 6.0.1 Marshmallow custom firmware is working with AT&T Samsung Galaxy S3. Do not install it on any other device or incorrect variant. Check the model number of your phone before going ahead.

Things To Remember:

Data Backup: Take a full backup of all your important data and settings like contacts, pictures, videos, music before proceeding to the rooting instructions.

Download and install USB drivers for AT&T Samsung Galaxy S3.

Enable USB debugging option on your device: Settings > Development Options > USB debugging.

Samsung Galaxy S3 must be rooted, unlocked and installed with a recovery tool like TWRP or CWM.

Make sure that the battery level of your AT&T Samsung Galaxy S3 should be at least about 60-70 charged to avoid unexpected shutdowns during the rooting process.

Download Files

  1. Download CM 13.0 Nightly ROM
  2. Download Google Apps (GApps)

Steps to Install CM 13.0 Android 6.0.1 Nightly ROM on AT&T Galaxy S3:

Step No 1:- Download the CM13 Android 6.0.1 (cm-13.0-20160609-NIGHTLY-d2att.zip) custom firmware on the desktop of your PC for Galaxy S3 AT&T from the above link. Do not unzip the firmware zipped file.

Step No 2:- Plug the phone to the PC via its USB data cable.

Step No 3:- Transfer the CM13 Nightly custom ROM .zip file to the root folder on SD card of your phone.

Step No 4:- After transferring ROM file, unplug the USB cord and turn it OFF to boot into Recovery Mode.

Step No 5:- Turn ON the phone while pressing and holding Volume Up + Home + Power buttons at the same time.

Step No 6:- While your Galaxy S3 is in Recovery Mode, perform wipe data tasks by navigating to the main menu of recovery and choose wipe data / factory reset and confirm the process.

Step No 7:- Now, go back to Recovery menu and select choose zip from sdcard -> Install zip from sdcard. Find the Android 6.0.1 Galaxy S3 custom ROM file that you have already downloaded it in Step No 1. Confirm the flashing process to begin.

Step No 8:- Once again, go back to main recovery menu and reboot your Galaxy S3 AT&T into the new custom ROM. Your device may take about 4 to 5 minutes to boot for the first after installation.

Step No 9:- Repeat the above process to install Google Apps package on your smartphone.

Tell us in the comments area below about your experience with this Android 6.0.1 Marshmallow custom firmware for Samsung Galaxy S3.

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