XUL: XML user interface language, or XUL, (pronounced as "Zool") is a mark-up language developed by Mozilla, and is an XML application used to describe graphical user interfaces.

XUL： XML用户界面语言(XML User Interface Language)，简称XUL(发音同“Zool”)，是一种由Mozilla研发的标记语言，一个用于描述图形用户界面的XML应用程序。