winmd

A winmd file is a metadata file used by the Windows Runtime (WinRT). WinRT is an API layer in Windows that allows applications written in different programming languages to interact with each other and with the operating system. The winmd file contains information about the types, members, and namespaces exposed by a WinRT component. This metadata is crucial for interoperability, enabling tools and languages to understand and consume WinRT APIs without needing access to the original source code. For example, a C# application can use a winmd file to call a C++ WinRT component.

These files are typically generated during the build process of a WinRT component. They are distinct from the actual implementation DLLs or EXEs, serving solely as a contract or interface definition. Developers can examine winmd files using various tools, such as ILSpy or the .NET Reflector, to inspect the available WinRT types and their properties. The structure of winmd files is based on the Common Metadata Infrastructure (CMI), which is also used in .NET assemblies. This standardization facilitates the creation of interoperable components across the Windows ecosystem.