So you want to unroot your Galaxy S3 GT-i9300? This unroot method will get you back “completely back to stock” with no trace of rooting. If you are unrooting your Galaxy S3 GT-i9300 for warranty, go ahead and follow the instructions below as no one will be ever to tell you’ve rooted your phone.
For T-Mobile Galaxy S3 SGH-T989, please see How to Unroot T-Mobile Galaxy S3 SGH-T989!
For AT&T Galaxy S3 SGH-I747, please see How to Unroot AT&T Galaxy S3 SGH-I747!
Step 1. First, you will need to go to Samsung-Updates.com and download your desired Galaxy S3 stock ROM. Use the “Region” to find out which Galaxy S3 stock ROM you need and go ahead and download it.