Enjoy USB Mass Storage on Galaxy S3 GT-I9300
On Ice Cream Sandwich the USB Mass Storage has been deleted, you have to plug the Ice Cream Sandwich in Media Transfer Protocol. No doubt, there’re many benefits of Media Transfer Protocol but some of you comes back to preference and compatibility the reason all OS aren’t well-matched with Media Transfer Protocol (MTP), so if you use any third party app to share data, it’s messy. But if you own a Samsung Galaxy S3 model number GT-I9300, you can enjoy USB Mass Storage Now.
Thanks to XDA developer member Kopfgeldjaeger who made an app for Galaxy S3 to get USB Mass Storage, it will give the SD card of device on USB Mass Storage. If you wish to get the device’s SD card on USB Mass Storage download the app from here to mount the SD card as USB Mass Storage.
You can install the apk file using a file manger app, I’ll recommend you to use the File Expert app to install the apk file, just download the app from above link and transfer it to the device SD card, then enable “Unknown sources” from Settings> Security. Then open the file manger app and navigate to thje folder where you’ve copied apk file, then tap on it to start flashing.
In the app you have both option to use USB Mass Storage (UMS) and MTP, please note that the app may not work on all computer like it may not work on a computer running the Linux operating system. Do let us know about your thoughts about the app in the below comment section and you can visit the original thread of XDA here, there you should thanks/donate the developer for this great effort that enables you to mount the SD card of your Galaxy S3 as UMS.