Extensible Application Markup Language

Extensible Application Markup Language (XAML, ⁱ/ˈzæməl/) is a declarative XML-based language developed by Microsoft that is used for initializing structured values and objects. It is available under Microsoft's Open Specification Promise. The acronym originally stood for Extensible Avalon Markup Language - Avalon being the code-name for Windows Presentation Foundation (WPF).

XAML is used extensively in .NET Framework 3.0 & .NET Framework 4.0 technologies, particularly Windows Presentation Foundation (WPF), Silverlight, Windows Workflow Foundation (WF) and Windows Runtime XAML Framework and Windows Store apps. In WPF, XAML forms a user interface markup language to define UI elements, data binding, eventing, and other features. In WF, workflows can be defined using XAML. XAML can also be used in Silverlight applications, Windows Phone apps and Windows Store apps.

XAML elements map directly to Common Language Runtime object instances, while XAML attributes map to Common Language Runtime properties and events on those objects. XAML files can be created and edited with visual design tools like Microsoft Expression Blend, Microsoft Visual Studio, and the hostable Windows Workflow Foundation visual designer. They can also be created and edited with a standard text editor, a code editor like XAMLPad, or a graphical editor like Vector Architect.