For those of you who have Mac OSX, you can root your Galaxy S3 GT-i9300 using Heimdall. This method is pretty simple to do, a bit different from Windows method but gives you the same results.
For Windows, please see How to Root Galaxy S3 on Windows!
For Linux/Ubuntu, please see How to Root Galaxy S3 on Linux/Ubuntu!
For U.S. Canadian dual-core Galaxy S3, see this other Mac root method!
Step 1. Put your Galaxy S3 into download mode by holding down Volume Down, Center Home, and Power buttons together for about 10 seconds.
Step 2. When you see the warning screen, hit Volume Up to enter ODIN Download mode.
Step 3. Once in download mode, connect your Galaxy S3 to your Mac OSX computer/laptop using a microUSB cable.
Step 4. Download GalaxyS3RootMac.zip, you will find a folder called GalaxyS3RootMac in your Downloads directory with all the files you need for rooting your Galaxy S3.
Step 5. Double-click on the file heimdall-suite-1.3.2-mac.dmg to install Heimdall. Reboot your computer after installation is complete.
Step 6. You should now find Heimdall-frontend app in your Application folder, double-click on it to run. Choose “Flash” then “Browse” and choose the file “s3pit.pit” in GalaxyS3RootMac folder.
Step 7. Click on “Add”, change Partition Name to “RECOVERY”. Then choose “Browse” and select the file “recovery.img” in GalaxyS3RootMac folder.
Step 8. Hit Start to begin the process.
If you get errors with Heimdall and you installed Kies for Mac, try this
in terminal to fix:
sudo kextunload -b com.devguru.driver.SamsungComposite
sudo kextunload -b com.devguru.driver.SamsungACMData
sudo kextunload -b com.devguru.driver.SamsungACMControl
Step 9. You should be able to flash the recovery image, your phone will then reboot.
Step 10. Connect your Galaxy S3 as a disk drive and copy the file CWM-SuperSU-v0.87.zip from GalaxyS3RootMac folder to anywhere on your Galaxy S3. If you don’t know how to connect your Galaxy S3 to your Mac OSX, see How to Connect Galaxy S3 to Mac OSX as Disk Drive.
Step 11. Reboot into ClockworkMod Recovery by holding down Volume Up, Center Home, and Power button together for about 10 seconds.
Step 12. Once in ClockworkMod Recovery, choose “install zip from sdcard”.
Step 13. Next choose “choose zip from sdcard” or “choose zip from internal sdcard” depending on where you put the file in Step 11.
Step 14. Choose CWM-SuperSU-v0.87.zip.
Step 15. Choose “Yes”.
Step 16. Once it’s done flashing the file CWM-SuperSU-v0.87.zip (the Superuser zip file), simply reboot and enjoy a fully rooted Galaxy S3.
Step 17. You will find SuperSU app once rebooted.
Step 18. You can now run rooted apps!
Q: Does this root method erase my settings and apps?
A: No, it doesn’t touch a thing, very safe to do.
Q: I ended up in Kernel panic mode, what do I do?
A: Relax, that’s same as ODIN download mode, simply run Heimdall again and flash the files again, it will work.
Q: I don’t get ClockworkMod Recovery like you do, just get Android with belly open.
A: If you’ve updated to newer software update, the stock OS will over-write ClockworkMod Recovery on reboot. To fix this, make sure “auto-reboot” is checked off in ODIN, then take the battery out when it’s done flashing in ODIN. Then enter ClockworkMod Recovery right away.
More questions? Please leave in the comment section below for help from author and other users.
More on this Root Method
This root method simply installs ClockworkMod Recovery to the recovery partition and installs Superuser zip file, very safe to do. With Galaxy S2, recovery partition was part of the kernel and was a bit dangerous but with Galaxy S3, Samsung has made recovery parition separate from the kernel, making it much safer just like how Galaxy Nexus works.