It is pretty cool if the developer knows the URI scheme so that the application can be initiated from inside another application, but it is even cooler to disassemble the default YouTube application itself and attempt to integrate Microsoft-built capabilities in your own application. video MediaContentFormat3 – MP4 video And with enough information (e.g. video feed from YouTube) I can easily build an alternative YouTube application (there is one already, by the way) as long as I have access to video IDs.