Microsoft Silverlight is a browser plugin that allows web applications to be developed with features like animation, vector graphics, and audio-video playback - features that characterize a rich internet application. Silverlight competes with products such as Adobe Flash, Adobe Flex, Adobe Shockwave, Java FX, and Apple QuickTime. Version 2.0 of Silverlight provides additional capabilities, including advanced interactivity features. Significantly, version 2.0 allows developers to use .NET languages and development tools when authoring Silverlight applications.

Silverlight was developed under the codename Windows Presentation Foundation/Everywhere (WPF/E). It is compatible with multiple web browser products used on Microsoft Windows and Mac OS X operating systems. Support for the Linux operating system by the third-party Moonlight runtime is under development.