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XML User Interface Language

XUL
Paradigm Declarative (markup language)
Developer Mozilla Foundation
Implementation language C++
Platform Gecko
OS Cross-platform
License MPL
Filename extensions .xul
MIME type: application/vnd.mozilla.xul+xml
Website https://developer.mozilla.org/en-US/XUL
Major implementations
Mozilla
Influenced by
HTML, XML

XUL (/ˈzl/ ZOOL), which stands for XML User Interface Language, is a user interface markup language that is developed by Mozilla. XUL is implemented as an XML dialect; it allows for graphical user interfaces to be written in a similar manner to Web pages.

XUL can be used to write cross-platform applications such as Mozilla Firefox, where it is interpreted by the layout engine, known as Gecko, which renders Firefox's user interface and Web page display.

In August 2015, Mozilla announced that the use of XUL for creating Firefox add-ons would be deprecated in the future in favour of WebExtensions.Pale Moon, a fork of Firefox for Windows and Linux, will continue to support XUL indefinitely.Waterfox, another fork of Firefox for Windows, macOS, and Linux is planning continued development of an XUL-based browser starting from the last XUL version of Firefox released by Mozilla.

XUL relies on multiple existing Web standards and Web technologies, including CSS, JavaScript, and DOM. Such reliance makes XUL relatively easy to learn for people with a background in Web programming and design.


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