XAML.io now compiles C# + XAML into native Windows, macOS, and Linux apps entirely in the browser. XAML.io is a free, browser-based XAML designer and C# editor built on top of the open-source OpenSilver framework.
Developers can use XAML.io to design UIs visually, edit code, and run .NET projects entirely online. It produces a Visual Studio project that can be downloaded and edited offline using fully open-source technologies. The developers say you can think of XAML.io as a frictionless on-ramp to .NET development, not a walled garden.
The updated version 0.7 of XAML.io can now compile a C# + XAML project into a native desktop application for Windows, macOS, and Linux without leaving the browser. The entire packaging pipeline, including packaging, file generation, and macOS ad-hoc code-signing, runs client-side in WebAssembly. No code is uploaded to a server.
All the developer has to do is to click Publish and pick a platform. Once published, which the Userware team says takes less than a minute, a self-contained .exe, .app bundle, or Linux executable is generated in the Downloads folder.
XAML.io already let developers write, compile, and preview .NET apps in the browser using the same XAML designer as OpenSilver. The new version has a single "Download as a desktop app" menu that will produce a ready-to-run executable for each of the three major desktop platforms: a Windows .exe, a macOS .app bundle, and a Linux executable. The apps are real native .NET processes built on .NET 10, not browser tabs wrapped in a shell.
The created app has DOM-based rendering. The WebAssembly part is only the IDE itself, and the desktop apps it produces are real native .NET 10 processes. The C# code is JIT-compiled by the runtime and runs in-process, with the same execution model as a WPF or WinForms app.
The UI is rendered as real DOM elements and is displayed inside the OS's built-in WebView via Photino. In the published desktop app the OpenSilver runtime is loaded directly by Photino through the OpenSilver.Photino bridge: there's no Blazor WebAssembly intermediate at runtime, and no client-side compilation either. This avoids the need for a bundled browser engine because Photino uses the OS's built-in WebView (Edge WebView2 / WKWebView / WebKitGTK) rather than bundling Chromium. The team says that keeps the download size to roughly the cost of the .NET runtime alone.
No source code leaves the machine because the work happens locally. The browser downloads only the shared runtime and launcher components; the compiled app itself is assembled in the browser tab.
"Signing a macOS app from inside a browser tab on a Windows PC sounds like it shouldn't work, and honestly we weren't sure it would until we saw it run,"
said Giovanni Albani, CEO of Userware, who added:
"There is no build server in the loop. Everything happens on the developer's own machine, in WebAssembly, so the source code never leaves it. That combination of native output and full privacy is what we're most proud of in this release."
The feature is currently in preview, and apps aren't yet signed with a publisher identity. This means there's no Apple Developer ID or Windows Authenticode, so standard first-launch prompts on macOS Gatekeeper and Windows SmartScreen still apply, and each download includes a short README with the steps to launch.
The developers say support for user-supplied code-signing certificates is on the roadmap. In this release, macOS targets Apple Silicon (arm64) and Linux targets x86_64.
XAML.io 0.7 is available now.
More Information
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