Rooting enables you to install apps which require root access and other custom ROMs. If you have updated Galaxy S 3 I9300 to I9300XXELKC Android 4.1.2 Jelly Bean Update. You should remember that rooting will void the warranty of your device which can be regained after installing official firmware.
The rooting of Galaxy S 3 on Adroid 4.1.2 is being made possible by CF-Auto-Root tool developed by a senior recognized XDA developer Chainfire.
Root Galaxy S 3 I9300 on I9300XXELKC Android 4.1.2 Jelly Bean
Make sure that the battery of device has a minimum charge of 60%.
Enable “USB debugging” on your device by going to Settings >> Developer options >> Enable USB debugging.
Download Rooting package from here (CF-Root-SGS3-v6.4.zip) and required Odin from here on your computer.
Extract the contents of both the zip files to a folder. After extracting Odin you will get “Odin3 v3.07.exe” file.
Switch off device and boot into download mode. Press Volume up, Power and you will see a “warning’ message”. Release Power buttons and press ‘Volume up’ to enter download mode.
Connect device to computer. Odin will detect your device and ID:COM will turn yellow and a message appears saying “Added”. Re-install drivers if Odin fails to detect device.
Click on PDA Button and navigate to select “CF-Root-SGS3-v6.4.tar” file which you have extracted in earlier step.
Click on Start button in Odin to start flashing Android 4.1.2 Jelly Bean firmware. When flashing is complete you will get a PASS message.
Disconnect device from your computer.
Your device will reboot automatically.
Your Galaxy S 3 I9300 is rooted on I9300XXELKC Android 4.1.2 Jelly Bean firmware.