A new app has come out that allows unlocking the Galaxy S3 – so that it can be used with a SIM card of any carrier, as well as allowing you to install any stock ROM that you may want to install – by XDA Recognized Developer spocky12, called GalaxSim Unlock. Samsung started relocking unlocked devices a few weeks ago with one of the firmware updates, and this app lets you get around those checks by keeping the phone unlocked, and even works with the new leaked Jelly Bean firmware.

This is the best unlock method you can use short of actually paying a fee for an unofficial key, so GalaxSim is quite a useful app for those looking to unlock their Galaxy S3. Though do keep in mind that this needs root access to work. Also, since Samsung might put in a check in future ROMs to relock devices, this app may stop working later on, but the developer promises to update the app as and when required.

Here are a few important points about the GalaxSim Unlock app:

  1. This app is tested to work only with the international Galaxy S3 i9300. It might work on US variants but that is not guaranteed.
  2. The app works with any existing rooted ROM as well as the new leaked Jelly Bean firmware.
  3. The app allows you to backup and restore your EFS aka IMEI data, so that it can be restored later.
  4. Support for more devices may come out later on, but for now only the Galaxy S3 is supported.

Read on to find out how you can install the GalaxSim Unlock app to unlock your Galaxy S3.

Compatibility

This guide is compatible only and only with the international Galaxy S3, model number i9300. It’s not compatible with the US variants or any other device. Check your device’s model number in: Settings » About phone.

Warning!

The methods and procedures discussed here are considered risky and you should not attempt anything if you don’t know completely what it is. If any damage occurs to your device, we won’t be held liable.

How to Install GalaxSim Unlock on Galaxy S3 for SIM Unlocking

  1. First, make sure your Galaxy S3 is rooted and has BusyBox installed. This won’t work without root access. To make sure you have BusyBox installed, use the BusyBox Installer app from the Play Store to install BusyBox.
  2. Download the GalaxSim app’s APK file from the source page.
  3. Copy the .apk file downloaded in step 2 to your device.
  4. Enable “Unknown sources” under the Settings » Security menu on the device, so that you can install apps from the SD card.
  5. You’ll need a file manager to browse through SD Card. You can install OI file manager or ES File Explorer or any other file manager app from the Play Store if needed.
  6. Open file manager and navigate to where you transferred the APK file in Step 3. Tap on the file to begin installation procedure and it will be installed in less than a minute.
  7. After the installation is complete, run the GalaxSim Unlock app on your phone. When it runs, grant it root access by pressing the Grant/Allow button.
  8. First, select the Backup EFS button to backup your EFS/IMEI data. This is a necessary step as it will help you restore your original IMEI data if something goes wrong.
    Your EFS/IMEI data is backed up to the GalaxSimUnlock folder on your internal storage. Do not delete this folder, and also make a backup of it on your computer for safekeeping.
  9. Then, press the Unlock button to unlock your Galaxy S3. After the procedure is complete, reboot the phone, after which your Galaxy S3 will be unlocked for use with any SIM card.

Your Galaxy S3 is now unlocked and can be used with any SIM card of you choice, and you can also install any firmware that you wish to. Do let us know how it works!