I bet this uses their undocumented API that allows uploads of media. If you use a traffic sniffer / HTTP Debugger like Charles, and use the Instagram app on yo

I bet this uses their undocumented API that allows uploads of media. If you use a traffic sniffer / HTTP Debugger like Charles, and use the Instagram app on your mobile device, you'll see that the native app is also using it's own API to upload media.