UWP Support for WinUI 3

[zhh135]

Hi everyone,

I'd like to reopen the discussion about WinUI 3 support for UWP apps. The official stance has been clear for a while: WinUI 3 is primarily designed for classic Win32 desktop apps (via Windows App SDK), while UWP is in maintenance mode, and WinUI 2.x is recommended for existing UWP projects.

However, the community has recently discovered that the reality is more nuanced – WinUI 3 actually contains native, built‑in support for the UWP application model. It’s not a missing feature; it's simply gated by a registry check during Application activation. By toggling that switch, WinUI 3 apps can run on UWP without any external patches or hooks, and they work perfectly – with full functionality and stability, as confirmed by several developers who have tested it.

So the technical foundation is already there. The support was never removed from the codebase; it was just disabled at runtime via a policy decision.

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The changing UWP landscape

I also recognise that the UWP ecosystem has shifted significantly:

• Xbox has explicitly moved to the GDK (Game Development Kit), and new UWP games are no longer accepted on the Xbox Store.
• HoloLens hardware is discontinued, and Windows Mixed Reality will stop receiving updates and support after November 2026.
• IoT devices using UWP have also been deprecated.

These changes mean that the "universal" vision of UWP is no longer the driving force. But that also raises a question:

Could UWP now be re‑evaluated not as a "cross‑device universal platform", but as a local application container that offers specific benefits – such as lifecycle management, sandboxing, secure store distribution, and a well‑defined activation model – for developers who still rely on those features?

We are not asking to revive the old "UWP everywhere" dream, nor to shift the primary focus away from Win32. Instead, we would like to ask:

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Questions for the team and the community

1. Given that the native support already exists (only gated by a registry flag), would the team consider officially re‑enabling it – at least as an experimental or opt‑in feature – in a future Windows App SDK / WinUI 3 release?

2. With the OSS momentum, would the project be open to community contributions that clean up and formalise this UWP path, provided we can provide sufficient testing and documentation?

3. For developers who have existing UWP codebases and want to move to WinUI 3, what is the recommended long‑term strategy? Should they rely on the unofficial registry tweak, or is there another official migration path planned?

It's worth noting that .NET 9 still offers preview support for UWP, which creates a somewhat contradictory picture – the runtime/platform is evolving, while the UI framework pretends UWP doesn't exist.

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Why this matters

Acknowledging and enabling this already‑present capability would:

• Save developers from resorting to unsupported hacks, reducing fragmentation and compatibility risks.
• Provide a smoother, official upgrade path for those who still depend on the UWP application model (e.g., for enterprise line‑of‑business apps, store distribution, or sandboxing).
• Strengthen the overall WinUI ecosystem by offering more choice, without compromising the Win32 focus.

I'm genuinely excited about where WinUI 3 is heading, and I believe that unlocking this dormant feature would only make the platform more inclusive and practical.

I look forward to a constructive and respectful discussion. Thank you!