XML User Interface Language (XUL)

Last Updated: May 29, 2020

Definition - What does XML User Interface Language (XUL) mean?

XML User Interface Language (XUL) is an interface markup language developed by Mozilla that enables developers to design applications that can run in both online and offline modes. XUL was introduced by Netscape in 1997 as part of what eventually became the Mozilla codebase.

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Techopedia explains XML User Interface Language (XUL)

XUL is based on the core existing web standards - CSS, DOM and JavaScript. XUL relies on Gecko implementations, and, hence, it is not interoperable with non-Gecko standards. XUL does not have any formal specification. Widgets running on the Mozilla platform can be developed using XUL and ported across different platforms. Components of XUL documents include:

Content: The arrangement of UI components is defined in the documents that together constitute the contents of XUL files.
Skin: Skin is regarded as the customizable set of colors or patterns that can be associated with a given XUL user interface defined in the form of skin files. It may include CSS and image files.
Locale:Language changes can be incorporated in the user interface using internationalization and localization features provided by XUL.

XUL files contain both XML and HTML elements in addition to XUL elements defined using the XUL namespace. A MIME type text/xul can be associated with XUL documents. An XUL interface defines a mechanism for programming a set of disconnected widgets. Simple scripting can be used like JavaScript, or complex C++ code can be used to define widget behavior.