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Microsoft to unify Windows desktop and UWP apps with new Project Reunion

Microsoft to unify Windows desktop and UWP apps with new Project Reunion


The latest twist and turn for Microsoft’s universal apps

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Microsoft has been working to bring win32 desktop apps and its Universal Windows Platform (UWP) apps closer together in recent years. That work has an official name now: Project Reunion. It’s the latest twist in Microsoft’s promise of universal apps that run across multiple Windows 10 devices, and Microsoft is now referring to traditional desktop apps and UWP ones as simply “Windows apps.”

“The idea behind Project Reunion is that it allows developers to build one Windows application and target all 1 billion Windows devices,” explains Rajesh Jha, executive vice president of Microsoft’s Experiences and Devices Group. “We’re bringing together the combined power of win32 and UWP so developers no longer have to choose because we’re unifying these existing APIs and in some way decoupling them from the OS.”

Microsoft is combining existing win32 and UWP APIs to make it easier for developers to build a Windows app. Existing apps can be updated and modernized, and APIs are being decoupled from Windows. “As we decouple existing APIs and add new APIs, we are also doing the work to polyfill as needed so the APIs work down-level across supported versions of Windows,” says Kevin Gallo, the director of Windows developer platform at Microsoft.

WinUI 3
WinUI 3

In simple terms, this means developers can now build a Windows app that takes advantage of the latest Windows 10 features without having to worry about older versions of the OS. Before, developers would typically wait until Windows 10 users were on the latest version of the OS before they updated their apps for new features. Now, they can pull that new API from NuGet, an open-source package manager, and compile it as part of their apps and not have to worry about old versions of Windows 10.

A big part of Project Reunion is WinUI 3, a UI framework that allows apps to have a modern UI that can scale across devices. Microsoft is also introducing a WebView2 preview today, which will allow developers to embed a Chromium-based WebView in their apps. WebView 2 will be completely decoupled from Windows, so developers can enable full web functionality without being locked into a particular version of Windows 10.

Microsoft also has broader ambitions for Project Reunion apps that go beyond just Windows. Modernized apps will run well on physical Windows machines, but they can also be optimized to be streamed from the cloud through Windows Virtual Desktop or remote app solutions.

“You’re now running Windows not only on Windows, but iOS, Android, Mac, and Linux from the cloud,” explains Jha. “Our hope with Project Reunion is that we can work with this incredible community of ours on Windows to further accelerate innovation and new experiences on Windows 10 to this first billion of users and the next.”

Businesses have been streaming apps remotely to iOS and Android for years, but the hope is that Project Reunion will ease the process by modernizing older apps instead of having to rewrite them for the web, iOS, or Android.