It’s funny how you find things when you’re not looking for them, in the case that you require to know which OS is your client running, there’s a pretty cool system class by the name of Capabilities in AS3 that handles this.

import flash.system.Capabilities;

trace("my Operative System is "+Capabilities.os);


You can also use it to find out the running Flash player version (down to Flash Player 6), test media decoders and even screen resolution, the values can also be sent from the server via GET and POST methods. You can read up properties in here: here