Reactor is built on WinUI and offers a new way to create the same native interfaces directly in C#, without having to write XAML.
By Frank Ulom
·
Published on October 24, 2026
·
5 min read
Microsoft has moved to clarify that it has no plans to discontinue WinUI or XAML following the launch and testing of an experimental framework called Microsoft.UI.Reactor. Given Microsoft’s history of abandoning UWP and shutting down Silverlight, it is hardly surprising that many developers have concerns.
According to reports, WinUI is Microsoft’s native user interface framework. Applications developed with it generally follow Windows 11’s design guidelines, with the Settings app serving as a typical example. XAML, meanwhile, is a markup language developers use to describe application interfaces.
Reactor is built on WinUI and offers a new way to create the same native interfaces directly in C#, without having to write XAML. It is therefore clear that Reactor is not intended to replace WinUI. However, this has prompted speculation about whether it could be the final blow to XAML, which has felt neglected for many years.
WindowsLatest sought clarification from Microsoft, which directed the publication to a new document and related open-source materials. Alexandre Zollinger Chohfi, from Microsoft, wrote in a developer blog post on 21 October: “WinUI is the underlying foundation. XAML is the mainstream way of using WinUI and will not be deprecated. Investment in it is ongoing.”
It is somewhat ironic that Microsoft has had to issue a specific clarification on the matter, but the move is a sensible one.
After Silverlight and UWP, Developers Have Good Reasons to Be Cautious
Microsoft has a long history of discontinuing products. Support for Silverlight ended on 12 October 2021. Although UWP is technically still maintained, Microsoft no longer uses it to develop new applications, and its official documentation states that it is “no longer actively developed”. It would not be unreasonable to say that the platform has effectively reached the end of its life.
Indeed, Microsoft’s original vision for Windows — “one app, adapted to all devices” — has long since fallen short of expectations.
Microsoft now recommends that developers use the Windows App SDK and WinUI when building new applications.
The industry has also witnessed Microsoft heavily promote several projects before subsequently abandoning them. Examples include Project Astoria, which was intended to bring Android applications to Windows; the Windows Subsystem for Android; and its iOS porting bridge projects. Windows Phone is another notable example.
Although Silverlight, UWP and WinUI serve different purposes, these experiences help explain why developers become apprehensive whenever Microsoft announces a new framework. There is insufficient reason to assume that today’s Microsoft will behave differently from the company of a few years ago.
Furthermore, Microsoft has recently undertaken company-wide restructuring aimed at cutting costs and increasing investment in artificial intelligence. This could once again reduce Windows’ priority within the company and hinder the ongoing recovery of the Windows ecosystem.
Microsoft Says It Will Continue Developing WinUI
Earlier this year, Microsoft made a similar commitment, at least regarding WinUI. At Microsoft’s Build 2026 developer conference, Chris Anderson said the company had “no plans to develop an entirely new framework”.
Microsoft has even begun referring to WinUI 3 simply as WinUI to prevent developers from assuming that WinUI 4 is imminent and delaying their adoption of the existing version while waiting for a new release.
The approach is intended to demonstrate continuity in the technology, much like the strategy behind Microsoft 365. Users do not wait every year for Microsoft 365 v2 because they understand that the product will continue to evolve through regular updates. There is no need to wait for a major version release before adopting it.
Microsoft followed a similar approach during the Windows 10 era, when it claimed that Windows 10 would be the final version of Windows before eventually changing its position.
This approach also presents challenges for hardware manufacturers. As Windows has moved towards a service-based model, existing computers can continue receiving new features, reducing users’ incentives to purchase new hardware.
Reactor Changes How Developers Build WinUI Applications
Why, then, is Reactor worth paying attention to?
Not every project launched by Microsoft has ended in failure, and Reactor could represent a positive development. If it progresses successfully, the Windows platform could see more native applications, potentially allowing users to move away from the large number of applications built on WebView.
This is precisely what some developers have been waiting for. They include not only programmers who work exclusively on Windows but also developers familiar with frameworks such as SwiftUI, React and Jetpack Compose.
Developers who have used any of these frameworks still need to learn XAML when they move to a traditional WinUI project. In my view, this new approach, which aligns more closely with existing development practices, could bring about significant changes.
Developers accustomed to using XAML to build WinUI applications will recognise that interface state-management code and interface markup are often spread across multiple files, making some development tasks more complicated.
Reactor addresses this issue by allowing developers to write interface styles and component states together. Compared with XAML-based development, this can reduce the number of files required.
Another important point is that even when developers switch to Reactor and use C# to build interfaces instead of XAML, the underlying components remain native WinUI controls. These include text boxes, navigation views and other components.
Microsoft has assured developers that Reactor does not introduce a separate rendering engine or a browser-based interface. This is why WinUI remains unaffected and continues to serve as the underlying foundation of the experimental framework.
In the project’s GitHub documentation, Microsoft states: “Reactor is not a new UI platform; it is simply a new way to describe WinUI content.”
One developer expressed strong support for the initiative, commenting: “My first reaction was, ‘It’s finally here.’ I hope it becomes widely adopted and makes native Windows development more accessible to developers from other technology stacks. It is difficult to imagine what the ecosystem would look like without all those bloated Electron applications.”
