The language used within stylesheets to transform or render XML documents. There are two W3C recommendations covering XSL stylesheets--XSL Transformations (XSLT) and XSL Formatting Objects (XSLFO).

(W3C) eXtensible Stylesheet Language. XSL consists of two W3C recommendations: XSL Transformations for transforming one XML document into another and XSL Formatting Objects for specifying the presentation of an XML document. XSL is a language for expressing stylesheets. It consists of two parts:

- A language for transforming XML documents (XSLT), and

- An XML vocabulary for specifying formatting semantics (XSLFO).

An XSL stylesheet specifies the presentation of a class of XML documents by describing how an instance of the class is transformed into an XML document that uses the formatting vocabulary.