microsoft/windowsappsdk

Windows App SDK is a set of tools and libraries from Microsoft that helps developers build desktop apps for Windows. It was previously known as Project Reunion. The goal is to give Windows developers access to newer Windows features and a modern visual style without requiring them to abandon their existing apps or rewrite them from scratch. The SDK includes WinUI 3, which is Microsoft's current user interface toolkit. It provides the visual building blocks for creating modern-looking Windows apps, following the Fluent Design guidelines that Microsoft uses across its own products. Developers can use WinUI 3 regardless of whether their app was originally built with the older Win32 API, Windows Forms, or WPF. One practical benefit is backward compatibility. Apps built with this SDK can still run on older versions of Windows 10, going back to a 2018 release called build 17763. This means developers can adopt new features without abandoning users who have not upgraded their operating system. The SDK is distributed as a NuGet package, which is a standard way of sharing code libraries in the Windows development world. Developers add the package to their project and can then call the new APIs alongside whatever framework they already use. There is no requirement to change the installer format for an existing app, though Microsoft notes some security and reliability benefits to using its MSIX packaging format. The repository is where the SDK's development happens in the open. Developers can file issues, ask questions, join discussions, and contribute code. Microsoft also maintains a companion gallery app called WinUI 3 Gallery that shows the available components and controls in action.