Small Bytes: WinUI 3 (Premium)

The Windows User Library (WinUI) 3 is a user experience (UX) framework for developers creating native apps for Windows 10/11. It is the successor to WinUI 2, which targeted the deprecated Universal Windows Platform (UWP), and it is delivered as part of the new Windows App SDK, which replaced UWP. WinUI 3 is also a Windows implementation of the Fluent Design System, a cross-platform design system that Microsoft uses to create consistent designs across its own apps on Windows, Mac, mobile, and the web.

WinUI 3 provides modern UI controls, styles, and capabilities to app developers and designers who target Windows. In addition to its inclusion in the Windows App SDK, WinUI 3 is also made available to developers who maintain legacy app codebases created with Windows Presentation Foundation (WPF), Windows Forms, or the Microsoft Foundation Classes (MFC) via a technology called XAML Islands. And it is available to developers who target Windows and other platforms via a single codebase using cross-platform solutions like .NET MAUI, React Native for Windows, or Uno.

Aside from its updated controls and styles---and given that the gap between the two will only grow over time as WinUI 3 is improved and WinUI 2 is not---WinUI 3 offers several other advantages over its predecessor. Because it is delivered with the Windows App SDK and not as part of Windows, it is versioned and updated separately from the OS, and it works with any supported version of Windows 10/11. It supports .NET and WebView2, whereas WinUI 2 did not. And the new apps one creates using WinUI are technically desktop apps and not mobile apps, as was the case with WinUI 2 (UWP).

To date, the biggest issue I’ve found with WinUI 3 is its accessibility. Adding WinUI 3 to existing desktop apps using XAML Islands is so complex that it’s basically a non-starter. (Even Microsoft has struggled with this, as I wrote recently in Microsoft is Moving File Explorer to the Windows App SDK. And very few developers would ever create a new app for only the Windows desktop today for obvious reasons, and those who do attempt this will discover that Windows App SDK development is very similar to that of UWP, which is not usually desirable. This leaves .NET MAUI (cross-platform mobile apps) and React Native (cross-platform web apps) as the more likely candidates, though in each case WinUI 3 is automatically provided (and only on the Windows version of the resulting app).

But you don’t need to be a developer to explore the modern UI controls and styles provided by WinUI 3 as anyone can download the WinUI 3 Gallery app from the Microsoft Store. Like many other Windows 11 apps, this app was built using a navigation bar, so it will be instantly familiar, and it provides interactive examples of all of the WinUI 3 controls and styles that are available via the latest version of the Windows App SDK, plus source code for each.

I’ll be writing about the Windows App SDK soon.