Various embodiments related to an application programming interface for user interface creation are disclosed herein. For example, one disclosed embodiment provides an application programming interface, embodied on one or more data-holding subsystems, comprising user interface creation services for intermediately defining a user interface including one or more user interface elements as declarative extensible markup language data. The application programming interface further comprises compiler services for providing aspects of the declarative extensible markup language data to one or more compilers for compilation into two or more different machine code implementations, where each machine code implementation is natively executable without a virtual machine by a different hardware platform to present the user interface intermediately defined as declarative extensible markup language data.