At Build 2020, Microsoft announced Project Reunion, a new project to make app development easier for Windows 10 platform. Project Reunion unifies access to existing Win32 (legacy Windows API) and UWP (Universal Windows Platform) APIs and makes them available decoupled from the OS, via tools like NuGet. Apps built using Project Reunion components can work across all the Windows 10 versions and devices.

Today Microsoft announced the first Project Reunion preview v.0.1.0.

The limited preview lays the foundation for Project Reunion’s runtime distribution and includes some of the work Microsoft has done towards creating the plumbing that makes sure apps can consume Project Reunion APIs.

More work is being done to unify the platform and to add more functionality such as Windowing and Storage APIs that will be released in the coming months, and do performance tuning.

Project Reunion will provide a common platform for new apps. Plus, it will help developers update and modernize your existing apps with the latest functionality, whether they’re C++, .NET (including WPF, Windows Forms, and UWP) or React Native.

The preview is not recommended for production use, but try out the samples, experiment with the APIs, and give us feedback.

Project Reunion principles:


Project Reunion works in all your apps – Win32, Packaged, and UWP – and across many versions of Windows.


Project Reunion supports your app’s use of modern software libraries for UI, AI, ML, packaging, frameworks, and libraries. Language projections for C++, Rust, C#, and JavaScript expand the benefits to all your apps. Cloud-backed apps, streaming, and edge-compute apps are all great places to use Project Reunion’s capabilities.


Project Reunion ships out of band with OS releases, with regular previews. You get to incrementally adopt Project Reunion components for your existing apps and middleware libraries using NuGet.


We’re committing to engineering Project Reunion in the open on GitHub, so you have a more direct say in how the platform evolves and can even help out.

Learn how to get started from Microsoft’s blog post here.