Root and Flash Samsung Galaxy S3 GT-I9300

Now! i will tell you How to Root & Flash the Samsung Galaxy S3 GT-I9300, lets read. and don't worry to try if you full follow this step and not ignore the Warning,. for anticipate if any problem you must back up! so you will more enjoy try this step!
According to Chainfire, the rooting method consists of two general steps. The first one is to flash an insecure kernel (based on XX NEE ALE8 firmware) via Odin3, after which your phone should be able to accept ADB root commands. Thereafter, su binaries must be installed (and, in this case SuperSU is used) so that your apps can enjoy superuser access.

Warning :

• The instructions in this guide are intended for use with the Samsung Galaxy S3, model number GT-I9300. Applying these instructions on another device or model may produce undesired outcomes.
• The information in this guide is provided for instructional and educational purposes only. There is no guarantee that these instructions will work under your specific and unique circumstances.
• Use these instructions at your own risk. We shall not hold any responsibility or liability for whatever happens to you or your device arising from your use of the info in this guide.
• Read and understand the whole guide first before actually performing the instructions.

Requirements :

• A Samsung Galaxy S3 GT-I9300
• A Windows PC
• Enable USB debugging on your device. You can do this through Settings > Developer options > USB Debugging.
• Backup all personal data on your phone to make sure you have a copy of your personal data (e.g., contacts, SMS, MMS, Internet settings, Wi-Fi passwords, and the like) in case the procedure in this guide erases such data.
• Samsung KIES installed on your computer. This is important as it will install the Galaxy S3′s device drivers.
• Odin3 1.85 installed on your computer (Odin3-v1.85.zip).
• Before you start the rooting process, make sure to disable Samsung Kies and any anti-virus and firewall software. This is to prevent them from interrupting the flashing process; interruption may lead to irreversible damage to your device.
• ADB (Android Debug Bridge) installed on your computer. You can get ADB by setting up the Android Software Development Kit (SDK) and downloading the appropriate component packages containing ADB.
• CF’s insecure kernel package (CF-Insecure-SGS3_XX_NEE_ALE8-v1.2.zip, 4.7 MB).
• Root package (sgs3-root-install.zip, 433.6 kB).

Flashing Insecure Kernel :

1. Extract the insecure kernel package on your computer to get the file CF-Insecure-SGS3_XX_NEE_ALE8-v1.2.tar.
2. Unzip the Odin3 ZIP file into a folder on your computer.
3. Double-click on the Odin3 executable program to launch it on your computer.
4. Turn off your Galaxy S3.
5. Boot the phone into Download Mode. You can do this by pressing and holding down the Volume Down, Home, and Power buttons until the screen turns on. Press Volume Up to enter Download Mode.
6. On the Odin3 window, click on the PDA button.
7. Search for the CF-Insecure-SGS3_XX_NEE_ALE8-v1.2.tar file and select it.
8. Do not make any other changes to Odin. Leave the selected options as they are.
9. Connect your phone to your computer. On the Odin3 window, you should see an “Added!” message in the lower left corner. This means that your phone was able to connect properly with your computer.
10. If you do not receive this message, disconnect your phone and try to reinstall the device drivers. You may also try using another USB port on your computer.
11. Click on the Start button in Odin3 to begin flashing the kernel.
12. When flashing is complete, you’ll see a “PASS” message with a green background in the uppermost left corner of the Odin window and your Galaxy S3 will automatically reboot.
13. If Odin seems to freeze or you receive a “FAIL” message with a red background, do the following:
    1. Disconnect your Galaxy S3 from your computer.
    2. Close Odin.
    3. Remove your Galaxy S3′s battery.
    4. Re-insert the battery.
    5. Repeat from step 5.

Installing Root and SuperSU : 

1. Extract the contents of the rooting package using WinRAR, 7-Zip, or other file extraction programs.
2. Go to the location where you installed Android SDK.
3. Open the platform-tools folder in the android-sdk folder. Typically, the location would be C:\Program Files(x86)\Android\android-sdk (or Program Files on 32-bit computers).
4. Copy the extracted contents of the rooting package to the platform-tools folder.
5. Make sure that you’ve enabled USB Debugging on your device.
6. Go to the platform-tools folder and double-click on install.bat to begin rooting your device.
7. The phone will automatically reboot during the procedure and after rooting is complete.

Yeah, your Samsung Galaxy S3 GT-I9300 has been ROOTED!! Congratulation.