This tutorial uses the Root Exploit package released by Senior XDA-Developers, k1mu. The Root Exploit package allows Galaxy S3 users to root their devices easily without tripping the KNOX warranty void counter.
Disclaimer: We and the developer of this rooting procedures shall not be held responsible if any undesirable outcomes may happen to your device. use of this root guide is solely at your own risk!
Note: This method will NOT set the KNOX warranty void flag. It will set the "Custom" flag, but that's nothing to worry about.
1. Install USB Drivers for Samsung Galaxy S3 on the computer.
2. Enable USB Debugging Mode on the phone. Go to Settings >> About Phone. Tap on Build Number several times till the message shows "You are now a Developer". Enable USB debugging by navigating to Settings >> Developer Options.
3. Make a backup of all your important data before following the guide.
4. Ensure the battery of the phone is charged more than 80 percent.
5. The Root Exploit package works only on the T-Mobile version of the Galaxy S3 with model numbers SGH-T999 (3G) and SGH-T999L (LTE). Applying this to any incorrect variant might brick the device. Verify the model number of the Galaxy S3 by navigating to Settings >> About Phone.
1. Root Exploit (saferoot.zip) - Mirror Link
Steps to Root Galaxy S3 (T-Mobile) SGH-T999/T999L Running on Android 4.3 Jelly Bean
Step 1: Extract the Root Exploit package to the computer using WinRAR/7-Zip/WinZip or any other extracting tool.
Step 2: Connect the Galaxy S3 to the computer using USB cable.
Step 3: On the computer, navigate to the extracted directory and double click "install.bat" file. You will see command prompt window which will detect your device and automatically run the scripts.
If you are using Linux or Mac OS X, navigate to the extracted directory in a terminal and run the following command. Please note that you'll need to have the Android Debugging Bridge (adb) installed and configured on your path.
$ chmod +x install.sh
Step 4: Once the rooting procedure completes, your phone will reboot automatically.
That's it! Samsung Galaxy S3 (T-Mobile) SGH-T999/T999L running on Android 4.3 Jelly Bean is now rooted successfully. You can now install any app that requires root permission. Verify the root status of the device by downloading Root Checker app from Google Play Store.
Note: Many Samsung devices store a flash counter that keeps track of how many times you have flashed custom firmwares to your device. Triangle Away can be used to reset the flash counter to zero.
How to Fix "Unfortunately, SuperSU has stopped"?
Step 1: Download and install the latest APK of SuperSU on your device.
Step 2: Open SuperSU app (update the binary if prompted) and allow it to disable KNOX.
Step 3: Reboot your device.
Thank's to all fellas at XDA who first tried out this rooting technique. This method was originally posted via XDA-Developers original thread.