Update Galaxy S3 I9300 to Android Marshmallow via AOSP Custom Rom


Google has recently announced the new Marshmallow firmware for some of the Android devices. Unfortunately Galaxy S3 was not in the list but don’t get disappointed guys because still you can Update Galaxy S3 I9300 to Android Marshmallow via AOSP Custom Rom. Yes, you can update your Galaxy S3 to 6.0 Marshmallow via AOSP Custom Rom. Credit goes the famous XDA Developers who provide Marshmallow based AOSP custom rom. As it is an AOSP Rom so, it will give you a pure Android experience. You will experience a pure Android 6.0 Marshmallow firmware like in the Google’s Nexus device. This will result in the faster performance of your phone. You will get rid of the laggy Galaxy UI.

The AOSP Marshmallow rom is not official, it is a custom rom ported for Galaxy S3 I9300 and is based on the 6.0 Marshmallow firmware. You may face some minor bugs like malfuctioning of some features but it will fix in future updates of this Rom.

So lets begin to Update Galaxy S3 I9300 to Android Marshmallow via AOSP Custom Rom. For installing this firmware you will need to install a custom recovery on your device. You can refer to the link below if you have not installed the custom recovery on your Galaxy S3.

Install CWM Custom recovery on Galaxy S3 I9300

For installing the AOSP Marshmallow custom rom on Galaxy S3 follow the instructions below. Also read the disclaimer and instructions before proceeding.

Galaxy S3

AOSP Marshmallow Rom for Galaxy S3 I9300

Galaxy S3 owners can enjoy the latest Marshmallow rom on their device via AOSP Custom rom. The Galaxy S3 will not get the official 6.0 Android M update. The AOSP rom is based on pure Android UI. You will get a nexus like feel on your device. This will result in faster performance and better battery performance. So, get ready to install AOSP Android Marshmallow rom on your phone. The tutorial to install Android Marshmallow AOSP Rom on Galaxy S3 is given below.


  • This method is only for Galaxy S3 model no I9300. Do not try this on any other model or phone. This process is for advance users only who are familiar with this process. If something wrong happens with your device while doing the process or after the process then Droidopinions.com will not be held responsible. So, try this at your own risk. Thanks.

Necessary Instructions before Proceeding

  • First of all check the model of your Galaxy S3 by going to Settings>>About Phone>>Model No. Make sure its I9300 then proceed.
  • Backup all your important data like photos, videos, contacts etc or perform a full backup using a custom recovery so, that you may not loose your data.
  • Charge your phone Above 65% to avoid power failure issues during the process.
  • Your phone’s warranty will void because you are installing a custom rom not an official firmware.

Download Required Files

Android Marshmallow AOSP Rom for Galaxy S3 I9300

Google Apps

Update Galaxy S3 I9300 to Android Marshmallow via AOSP Custom Rom, Steps


  • First of all download the AOSP marshmallow rom and Google Apps from the links above on your PC. Do not extract them.


  • Now connect your Galaxy S3 to the PC and move the AOSP Rom and Google Apps to any folder of the phone storage.


  • After that turn off your Galaxy S3.


  • Enter into download mode by pressing and holding Home+Volume Up+Power button for few seconds and release when the recovery menu appears.


  1. In the recovery menu go down to the wipe cache partition with help of volume button and select and confirm by power button.
  2. Now go to the advance option of the recovery and select the option wipe dalvik cache and confirm.


  • Now go back to the main recovery menu. Go down to the option install zip from sd card then go to choose  zip from sd card and find the AOSP Rom that you have moved to your phone in the second step.


  • Select the rom and confirm the task to install it and wait until AOSP Marshmallow Rom is installed.


  • After the rom is installed, again choose zip from sd card and this time find the Google Apps that you have moved to your phone. Now select the Google Apps and confirm to install.


  • After the installation of both AOSP Marshmallow Rom and Google apps, go to the recovery menu and select the option reboot system now to restart your phone.


  • Your phone will restart then. At first your phone will take some time to show up the home screen. So, don’t panic. Enjoy the new Marshmallow Rom when you see the home screen.

Congratulations!!! you have successfully installed the AOSP Android Marshmallow Rom on your Galaxy S3. Navigate to Settings>>About Phone to check the Rom version. So, that was it, Hope you like our tutorial Update Galaxy S3 I9300 to Android Marshmallow via AOSP Custom Rom. If you have any questions feel free to ask in the comment section for answers.

Many of the times the device gets stuck at boot animation. For resolving this follow the instructions below.

Fix if device gets Stuck at Boot Screen

It is a common problem that device gets stuck at the boot screen after flashing a new rom or firmware. If you face this problem then you can resolve this by wiping data/factory reset from the recovery menu. Follow the instructions below to solve this problem.

  • Turn of the device if possible or you can also do this while on the boot screen. Press and hold home+volume up+power buttons for few seconds until recovery menu appears.
  • Now in the recovery menu go down to the option wipe cache partition and select it and confirm. Now again go down to the wipe data/factory reset and select and confirm.
  • Now select the reboot system now option to restart your phone.

By doing the above process your problem will be solved.

So, that is all for today guys. Now time to go,, //Bye

Please like, share and subscribe. Comment to share your views.