Earlier this month, Microsoft announced details about WinUI, its open source Windows 11 user interface framework. Open source WinUI has been a long-standing call from developers, but it's not easy to implement. Since WinUI is "entrenched" at the proprietary level of the operating system, open sourcing the framework requires a careful and thoughtful approach. Just weeks after its initial release, Microsoft is ready to share more information about the WinUI OSS project.
Microsoft hopes to accomplish this task in four phases. The first phase focuses on more internal contributions on GitHub. The second phase will allow developers to clone the repository and build WinUI locally. The third phase will allow third-party developers to contribute to the project, and the final phase will make GitHub the "primary place for development, issue tracking, and community engagement" and phase out internal repositories.
Currently, Microsoft developers are busy "unpacking" WinUI from the proprietary parts of Windows that cannot be shared publicly. Once Windows App SDK 1.8 is released later this month (currently in preview, with WinUI bundled with WASDK), developers will begin implementing pull requests on GitHub. Microsoft plans to complete the first phase in early October 2025.
As for allowing third-party developers to clone the code base and build locally, Microsoft said it is currently "actively exploring" the idea. This requires a more cautious approach, so expect it to be some time before the company releases more details. Here's the company's statement:
Since WinUI's release schedule is closely tied to the Windows App SDK, our branching strategy now allows us to start completing PRs in parallel with the upcoming WASDK 1.8 release. The 1.8 preview was released on August 19th and the stable version is about to be released, which gives us a good foundation to start integrating changes. Based on this, we plan to complete the first phase in early October.
Phase 2 is still being actively explored, and while we're being more cautious about it, we hope to share tangible progress soon.
You can follow the discussion about making WinUI open source on GitHub.