XBL or e X tensible B indings L anguage or X ML B indings L anguage is a language for linking elements of an XML document with behaviors, interfaces or content models.

XBL was created by Mozilla to define properties of XUL elements . The W3C is in the process of standardizing a second version of the specification, more generic and not compatible with the first.

An XBL file contains links describing element characteristics. In the framework of XUL for example, it is possible to describe the user interface and the behaviors of the basic elements, such as the scroll bars.

Version 1.0 of the standard was created by the Mozilla project. It is implemented in all software based on Gecko : Firefox , Thunderbird , SeaMonkey etc.