How to update Galaxy S3 I9300 to Android 5.1 Lollipop

Galaxy S3 update

Follow the step-by-step tutorial to update Samsung Galaxy S3 GT-i9300 to Android 5.1 Lollipop with unofficial CyanogenMod 12.1 ROM.

Galaxy S3 is no more officially supported for software updates by Samsung due to hardware limitations but there is nothing to be worried about it as you can still update Galaxy S3 to the latest version of Android using Custom ROM by CyanogenMod team.

Before updating your phone using Custom ROM, there are certain requirements you need to fulfill:

  • This ROM is only compatible with Galaxy S3 GT-i9300, do not flash it on another variant of Galaxy S3, it may brick your device.
  • Make sure phone is already rooted with CWM or TWRP recovery installed.
  • Go to Settings –> Developers options and enable USB debugging.
  • Take Nandroid backup of your existing rom using recovery.
  • Charge your phone to at least 50% level.
  • Custom ROM in its initial stages do have bugs and some features might not work properly.
  • Last but not the least, Proceed at your own risk.

These are the instructions on how to flash the Android 5.1 Lollipop ROM using custom recovery:

Step 1: First of download the CyanogenMod 12.1 ROM and GApps zip files for Galaxy S3 using the links given below:

Step 2: Without extracting copy the zip files to your phone.

Step 3: When you copy the files, Reboot into Recovery Mode. Here is how you can do it:

  • Switch Off your Galaxy S3.
  • Hold the Volume Up+Home+Power buttons simultaneously for a few seconds.

Step 4: Take Nandroid Backup of your phone.

For CWM Recovery – Select the ‘Backup and Restore’ Option and then Backup to your internal or external storage.

For TWRP Recovery – Tap the ‘Backup’ option and then Select the system partition files you want to Backup.

Step 5: Clear the system cache and factory reset it in order to prepare your phone for new installations.

For CWM Recovery – Select Wipe data/Factory Reset then Wipe Cache Partition then select Advanced->Wipe Dalvik Cache

For TWRP Recovery – Tap the WIPE  option, then Factory Reset and swipe to confirm.

Step 6: Now you can flash the ROM zip file.

For CWM Recovery – Select ‘Install Zip from SD Card’ and navigate to storage location and select the zip package.

For TWRP Recovery – Tap the ‘Install’ option and select the Custom ROM zip package.

Step 7: Once the ROM is successfully flushed , then use the same method, as in Step 5, and flash the GApps zip file.

Step 8: Finally when ROM and GApps packages are flushed successfully, Reboot your phone by heading to the main recovery options and ‘Reboot system now‘.

That’s it guys, I hope you’ve enjoyed this tutorial. Do let me know and share your experience in the comment section. It was really simple guide, however if you’re still confused at any point feel free to ask for further support and assistance.