UIML (User Interface Markup Language, German: User Interface Markup Language ) is a markup language based on XML that is used to make platform independent user interfaces. It is through the introduction of a general description of syntax to the modeler be given the opportunity to define the structure and the style of a user interface. Until subsequent automatic transformation of this model, the user interface, the concrete user interface is generated which (if there is a matching mapping stylesheet ) programming language is in any described. Be instantaneous as concrete user interfaces, inter alia, HTML, VoiceXML and Java Swing support. XML is typically used to store documents and data, but it can be used thanks to the general definition for other applications.

XML User Interface Language ( XUL ) provides similar functionality as UIML and is used by Mozilla among others, the Mozilla Firefox browser and the email client Mozilla Thunderbird.