WinUI 3 — Modern Native UI Framework for Windows Apps

Introduction

WinUI 3 is Microsoft's native UI framework for building modern Windows desktop and UWP applications. It provides the full Fluent Design System, XAML markup, and a comprehensive control library as part of the Windows App SDK, decoupled from the OS update cycle so developers can ship the latest UI components regardless of the user's Windows version.

What WinUI 3 Does

• Provides the official Fluent Design control library for Windows desktop applications
• Ships as a NuGet package via the Windows App SDK, independent of Windows OS releases
• Supports XAML markup and C#/C++ for building rich, accessible user interfaces
• Includes modern input handling with touch, pen, mouse, and keyboard support
• Renders UI using DirectComposition and Direct2D for smooth 60fps animations

Architecture Overview

WinUI 3 is the UI layer of the Windows App SDK (formerly Project Reunion). It sits on top of the Windows composition engine, using DirectComposition for GPU-accelerated rendering and XAML Islands for hosting modern controls. The framework decouples UI components from the OS by shipping as a redistributable package. Applications reference WinUI via NuGet, and the runtime resolves to the installed Windows App SDK version on the target machine.

Self-Hosting & Configuration

• Install Visual Studio 2022 with the Windows App SDK / WinUI workload or use the .NET CLI with WinUI templates
• Create a project using dotnet new winui3 or the Visual Studio project wizard
• Add controls via XAML markup or C# code-behind using the Microsoft.UI.Xaml namespace
• Package for distribution using MSIX for Store deployment or unpackaged for sideloading
• Customize Fluent theming through resource dictionaries and the Application.Resources section

Key Features

• Complete Fluent Design System with Mica, Acrylic, rounded corners, and smooth animations out of the box
• Rich control library: NavigationView, TreeView, InfoBar, BreadcrumbBar, and 60+ controls
• Hot Reload for XAML and C# during debugging for rapid UI iteration
• Accessibility built in with UI Automation, high contrast themes, and screen reader support
• Decoupled from OS releases so apps can use latest controls on older Windows 10 versions

Comparison with Similar Tools

• WPF — Mature Windows UI framework; WinUI 3 is its successor with Fluent Design and modern rendering
• UWP — Sandboxed app model with WinUI 2; WinUI 3 removes sandbox restrictions for desktop apps
• Avalonia — Cross-platform .NET UI; WinUI 3 is Windows-only but offers deeper OS integration and official Fluent Design
• Electron — Web-tech desktop apps; WinUI 3 is native with lower memory usage and OS-native look and feel
• MAUI — Cross-platform .NET framework that uses WinUI 3 on Windows but adds iOS/Android/macOS targets

FAQ

Q: Does WinUI 3 work on Windows 10? A: Yes. WinUI 3 supports Windows 10 version 1809 (build 17763) and later through the Windows App SDK.

Q: Can I migrate an existing WPF application to WinUI 3? A: WinUI 3 XAML is similar but not identical to WPF XAML. Microsoft provides migration guidance and XAML Islands for incremental adoption.

Q: Is WinUI 3 open source? A: Yes. The WinUI library (microsoft-ui-xaml) is open source under the MIT license on GitHub.

Q: Can I use WinUI 3 with C++ instead of C#? A: Yes. WinUI 3 supports both C# and C++/WinRT for application development.

Sources

• https://github.com/microsoft/microsoft-ui-xaml
• https://learn.microsoft.com/en-us/windows/apps/winui/winui3/