While it was possible to root international Galaxy S3 devices before, the XDA devs have found out a way to root carrier locked Galaxy S3 on Sprint, At&t and T-Mobile neworks as well. Head below for the step-by-step tutorial.
Disclaimer : Rooting will void you device’s warranty. Chiphazard will not be held responsible if your device gets harmed by following the tutorial below. Proceed at your own risk.
Part 1: Initial Setup
Step 1: Enable USB debugging [Settings > Developer options] and connect your device to PC via USB cable.
Step 2: Download CMW_SuperUser_v3.07.zip [Direct Link] and transfer it under the parent directory on your device’s internal storage and then disconnect your device and power it off.
Part 2: Flashing clockworkmod.tar
Step 3: Download Odin3-v3.04.zip [Direct Link] and run it.
Step 4: Download clockworkmod.tar [Direct Link].
Step 5: Boot your Galaxy S III into download mode by pressing and holding Volume Down, Home and Power buttons. Press Volume Up when the prompt comes up.
Step 6: Connect your Galaxy S III with PC once again. Odin should detect your device.
Step 7: Click on PDA and select the clockworkmod.tar file you downloaded in Step 4.
Step 8: Ensure that Auto Reboot and F. Reset Time are selected. Then, click on Start to begin process.
Part 3: Flashing SuperUser
Step 9: Now you must boot into ClockworkMod Recovery Mode. Shut down your device, press and hold Volume Up, Home and Power buttons.
Step 10: Navigate to install zip from sdcard > choose zip from sdcard > [CWM_SuperUser_v3.0.7.zip file you downloaded earlier]. After it’s done, choose reboot system now from main menu.
Part 4: Final Steps
Step 11: Install BusyBox from the Play Store. Grant it SuperUser permissions and follow on-screen instructions.
Step 12: Launch the SuperUser app from your app drawer and update binaries from [wrench icon] > Su binary > Update.
The method for rooting AT&T’s Galaxy S III involves the same steps as above but uses different files. Please be careful about using the correct files; you may brick your device otherwise.
Step 1: Follow Part 1: Initial Setup above.
Step 4: Follow the rest of steps orderwise.
For any query, headover to this LINK.