XAML Io

Overview

XAML.io is a groundbreaking browser-based development environment that brings visual .NET UI design to the web. Built by Userware on top of the open-source OpenSilver framework, it eliminates the traditional barrier of installing large SDKs and configuring development environments. Developers can navigate to xaml.io in any modern browser and immediately start building XAML-based applications using a professional visual designer, a full C# code editor, and an integrated runtime powered by WebAssembly.

Key Features

The platform combines several powerful capabilities into a single cohesive environment. Its visual drag-and-drop designer provides over 100 ready-to-use controls including complex widgets like data grids, charts, and input forms, all configurable through a familiar property panel. The AI-assisted UI generation feature is a standout capability -- developers can describe their desired interface in plain text and the AI generates complete, editable XAML layouts in seconds. The code-behind integration allows developers to write C# event handlers and application logic alongside their XAML markup in the Monaco editor. Projects can be run instantly in the browser with a single click, thanks to OpenSilver compiling .NET code to WebAssembly for native-speed execution.

Cross-Platform and No Vendor Lock-In

Every project can be downloaded as a standard Visual Studio solution (.sln) at any time. This means developers can start prototyping quickly in the browser and seamlessly transition to a full offline IDE for production development. The underlying OpenSilver framework is fully open-source under the MIT license. With version 0.7, XAML.io now supports native desktop export -- users can publish a self-contained .exe for Windows, a .app bundle for macOS, or a Linux executable, with compilation and packaging happening entirely within the browser.

Use Cases

XAML.io is ideal for rapid prototyping, allowing developers to go from concept to a working UI in minutes. It serves as an excellent educational tool for learning .NET and XAML, removing environment setup friction. Backend and AI engineers who need to quickly build front-end interfaces to demo models or APIs will find it especially valuable. The platform also works well for internal tools, proof-of-concept applications, and sharing interactive UI demos.

Pricing and Availability

XAML.io is currently free to use during its preview phase. No sign-up is required to start building, and all core features including the visual designer, AI assistant, C# editor, and cloud saves are available at no cost. The platform is built on OpenSilver, a free and open-source framework professionally supported by Userware and used by enterprises worldwide to modernize legacy WPF, Silverlight, and LightSwitch applications.