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Win32 APIs provide functionality that not all languages and frameworks support themselves. When developing for Windows, developers often call into Win32 APIs to access this functionality.

Historically, this has required manually redefining the APIs to make them accessible, which is fragile and error-prone. Community projects like (.NET) and (Rust) have taken on the burden of providing strongly-typed and validated API signatures for their frameworks, but the projects are manually maintained, which is hard to sustain and makes it challenging to provide thorough API coverage.

This project aims to provide metadata for Win32 APIs such that idiomatic projections and projects like the ones above can be generated for all languages and frameworks in a more automated way and with more complete API coverage.

To call Win32 APIs from the language of your choice based off of this metadata, use the following language projections:

Note: Community projects are listed here to help with discovery but are not officially validated by Microsoft.

See the roadmap and FAQ for more details.

If you'd like to browse the metadata to see what we're emitting, extract Windows.Win32.winmd from the Microsoft.Windows.SDK.Win32Metadata NuGet package and load Windows.Win32.winmd in ILSpy. Download the package and rename it to .zip to browse and extract its content.

ILSpy with winmd


Below are some principles that guide the metadata that we produce:

  • Provide the broadest API coverage possible
  • Keep the names of the original APIs, but express in metadata additional information that can make them easier to use.
  • Convert non-specific types like uint that use constants into explicit enums to improve usability and discoverability. Keep enum member names consistent with the original constant names to preserve SEO.
  • Express Win32 typedefs like HANDLE and GDI objects as strongly-typed structs. The definition of these structs include how to dispose of the resources (like CloseHandle or DeleteObject). It is up to language projections to make use of this information in a language-specific way. For example, a C# projection could use SafeHandle objects for HANDLE and GDI objects.









Windows SDK

  • All Windows headers (e.g. RecompiledIdlHeaders) and Interface Definition Language (IDL) files in this repository and in the aforementioned NuGet package.


This project may contain trademarks or logos for projects, products, or services. Authorized use of Microsoft trademarks or logos is subject to and must follow Microsoft's Trademark & Brand Guidelines. Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship. Any use of third-party trademarks or logos are subject to those third-party's policies.