Windows UI Library
The Windows UI Library is a set of NuGet packages that provide controls and other user interface elements for UWP apps. It also enables down-level compatibility with earlier versions of Windows 10, so your app works even if users don't have the latest OS.
The Windows UI Library contains new controls that haven't yet shipped as part of the Windows platform.
Updated versions of existing controls
The library also contains updated versions of existing controls that you can use with earlier versions of Windows 10.
Support for earlier versions of Windows 10
Windows UI Library APIs work on earlier versions of Windows 10, so you don't have to include version checks or conditional XAML to support users who might not be running the very latest OS.
Support for XamlDirect
XamlDirect enables you to use XamlDirect APIs on earlier versions of Windows 10 without needing to write special code to handle multiple target Windows 10 versions.
The Xaml Direct APIs, designed for middleware developers, gives you access to a lower-level Xaml features which provide better CPU and working set performance.
The dev branch of the Xaml Controls Gallery sample app has also been updated to use WinUI as a usage example:
How-to articles for Windows UI Library controls are located with the rest of our UWP controls documentation. We have articles for most of the new controls, and more articles are on the way.
API reference docs are located here: Windows UI Library APIs.
Install and use the Windows UI Library
For instructions, see Getting started with the Windows UI Library.
NuGet package list
The Windows UI Library contains multiple NuGet packages: Windows UI Library NuGet package list.