Update Galaxy S3 GT-I9300 To Android 5.1 Lollipop With CyanogenMod 12.1 Custom ROM

The Samsung Galaxy S3 has received a working CyanogenMod 12.1 ROM build. CM12.1 comes to the Galaxy S3 GT-I9300 variant from the same developer who made the original CyanogenMod 12 Android 5.0 ROM for this device.

The CyanogenMod 12.1 custom ROM for the Galaxy S3 GT-I9300 introduces the new Android 5.1 Lollipop Google version with stock Android skin. The experience is exactly the same as you would find on a Google device or other AOSP ROMs.

While the previous CyanogenMod 12 custom ROM was pretty much stable, CyanogenMod 12.1 is not as stable. Most of the things work on Android 5.1 too but there are a few bugs and issues. For example, hardware-specific functions like GPS, camera, graphics and audio are supposed to work while software-specific functions introduced by CyanogenMod 12.1 have yet to work without force-closing.

Still, this shouldn’t prevent power users from getting a taste of Android 5.1 on their devices, even though it is not official since there is no maintainer for the device.

Detailed Guide To Install Android 5.1 Firmware On Galaxy S3 With CyanogenMod 12.1 Custom ROM


Please note that this CyanogenMod 12.1 build is only for the Exynos International variant of the Samsung Galaxy S3 with build number of GT-I9300. Do not try to flash the ROM on other variants as it might cause damages to your phone. To check the model of your phone, go to Settings > About Phone.


CyanogenMod 12.1 ROM for Galaxy S3

Android 5.1 Google Gapps

Install Custom Recovery

How To Install Custom Recovery On Galaxy S3 (CWM, PhilZ, TWRP)

Flashing CyanogenMod 12.1

  1. Make sure to charge the phone to at least 50% so it doesn’t turn off and get damaged.
  2. If you have downloaded the required files on your computer, connect the phone and transfer the files to your Galaxy S3.
  3. Then press the power button and press “Shut Down” to turn the phone off.
  4. Press Volume Up + Home + Power buttons to boot into custom recovery.
  5. Select “Wipe Cache”, “Wipe Dalvik Cache” and “Wipe Data/Factory Reset”.
  6. Select “Install ZIP from SD Card”. Navigate to the folder where your ROM file is located and install it.
  7. Do the same thing with the Gapps file.

That is all. Now you have successfully installed the ROM and you will be able to enjoy Android 5.1 Lollipop CyanogenMod 12.1 ROM experience on your Galaxy S3 GT-I9300.


  1. Hey Man , thx a lot! , i’ve got everything right until cyanogenmod starts .. y pass the language, wifi, google, and after cyanogenmod account setting it says “unfortunately setup wizard has stopped”

    • It seems to be a common problem. Try installing only the ROM, then wipe dalvik cache and reboot. Complete the setup process. Boot into recovery and then flash Gapps.

  2. Hi Ronaldo
    Great guide, I’ll be trying it today! 😀
    Is there a list of bugs, and what is and isn’t working with this release?

  3. Can I transfer the files to my sd card instead of phone memory? Will I be still able to install Cyanogenmod!?


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