If you have already updated your Samsung Galaxy S3 to the latest official firmware Android 4.1.2 XXEMR2, you can now root your device using CF-Root with ODIN. In case you are not aware of the benefits, rooting Galaxy S3 I9300 will allow you to install root apps, install system tweaks and custom recovery.

CF-Root Package Details:

 - SuperSU v0.93

 - ClockworkMod (CWM) recovery v5.5

 - CWM Manager v3.60

However, it should be noted that the rooting package used in this tutorial does not install any custom recovery tools like ClockworkMod (CWM), which you will have to install separately.

Below is the complete guide on how to root Android 4.1.2 ZSEMB1 Jelly Bean on Galaxy S3 I9300. However, before you dive into the process:

-  Make sure your Galaxy S3 is on the Android 4.1.2 build ZSEMB1 firmware. The tutorial is meant for international variant Galaxy S3 I9300 model only and it does not work on any other devices. You can confirm the firmware from Settings > About phone.

- Make sure the USB drivers for Samsung Galaxy S3 are installed properly. If not, download the latest official drivers from here.

- Make sure you backup all your important data before you start the rooting. It's highly advised that you use custom recovery tools such as CWM or TWRP. Such tools create a complete image of your existing phone set up. Otherwise, you can backup your apps; SMS messages; contacts, Gmail and Google data (Sync with Google Sync), call history, and WhatsApp messages.

- Make sure your USB debugging mode is enabled on your device. You can do it by navigating to Settings > Developer Options or Settings > Applications > Development.

- Make sure your device has at least 80-85 percent battery charge.

Note:  - Users must note that the instructions given in this tutorial are applicable for reference purpose only and that MobilenApps cannot be held responsible if anything goes wrong. Proceed at your own risk.

The Procedure:

Step 1: - Download CF-Root-SGS3-v6.4.zip for Galaxy S3 on to your computer and extract the zip file.

Step 2: - Download ODIN v1.85 which is needed for installing Android 4.1.2 your device.

Step 3: - Switch your device off and then boot it into Download Mode. You can do that by pressing and holding the Volume Down and Home Buttons together, then press the Power Button until the construction Android robot icon with a triangle appears on the screen. Tap the Power Button once again to make sure you have entered into Download Mode.

Step 4: - Now, open ODIN on your computer, connect your computer while the device is in the Download Mode.

Step 5: Upon successfully connecting, one of the ID:COM boxes will turn yellow with the COM port number with the corresponding COM port number. This step may take a longer time, so be patient.

Step 6: Here you will have to select the root package file that you have to flash/install on your phone.  The root package can be found from the extracted file in Step 1. Click on 'PDA' and select the file CF-Root-SGS3-v6.4.tar.

Step 7: Now check the Auto Reboot and F. Reset Time options in ODIN. Make sure you DO NOT select any other options in the ODIN.

Step 8: Select the Start Button in ODIN. Here the firmware installation process will begin, it would take a few minutes to complete.

Step 9: Once the installation is complete, your phone will restart. You can unplug your device from the computer when you see the home screen.

At this point, you have successfully rooted Android 4.1.2 Jelly Bean (ZSEMB1) on your Samsung Galaxy S3 I9300. Check for the Superuser app in your apps list to verify the update.  Download and install the Root Checker app from Google Play Store to make sure you have correctly installed the above root method and it's working fine.

[Source: Team Android]