High Quality Content by WIKIPEDIA articles! XPIDL (Cross Platform Interface Description Language) is the interface definition language developed by Mozilla.org to specify XPCOM interfaces. It is similar to the Object Management Group's CORBA IDL. Mozilla provides a utility xpidl that converts the IDL files into XPCOM Type Library (.xpt) files. An interface description language (or alternately, interface definition language), or IDL for short, is a specification language used to describe a software component's interface. IDLs describe an interface in a language-neutral way, enabling communication between software components that do not share a language for example, between components written in C++ and components written in Java.