We're all puzzled by it too, but without a look at the source code we can't easily figure out what it's doing. I've not written a windows application in over a decade, but back then I read an MSDN page about this. As I understand it the application is supposed to declare that it either doesn't want any dpi scaling, that it supports dpi scaling, or that it supports dpi scaling but will handle the scaling itself. I believe that the compatibility setting only applies to applications in the second category; apps that handle dpi scaling themselves might still scale.