XSLT

Last updated April 23, 2026

XSLT (eXtensible Stylesheet Language Transformations) is a declarative language for transforming XML documents into other formats — another XML document, HTML, plain text, or JSON. An XSLT stylesheet is itself an XML document; given an input XML and a stylesheet, an XSLT processor produces the output. The language was designed alongside XPath in the late 1990s and has matured through versions 1.0, 2.0, and 3.0.

A minimal example

Transform a list of books into an HTML table.

Input:

<books>
  <book><title>Deep Work</title><author>Cal Newport</author></book>
  <book><title>Code</title><author>Charles Petzold</author></book>
</books>

Stylesheet:

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="books">
    <html>
      <body>
        <table>
          <xsl:for-each select="book">
            <tr>
              <td><xsl:value-of select="title"/></td>
              <td><xsl:value-of select="author"/></td>
            </tr>
          </xsl:for-each>
        </table>
      </body>
    </html>
  </xsl:template>
</xsl:stylesheet>

Applying the stylesheet produces a full HTML page with one row per book.

Why it matters

XSLT is one of the few declarative transformation languages that is widely deployed, open, and fully standardised. It is particularly strong at:

Document publishing. Transforming DocBook or TEI XML into HTML, ePub, or PDF source.
Data integration. Converting one XML schema into another across organisational boundaries.
XML report generation. Producing human-readable reports from structured data.
Bidirectional data mapping in legacy enterprise systems.

Why it is an acquired taste

XSLT is functional, template-based, and written in XML, which is a particular combination. Newcomers often find the syntax alien (“why am I writing <xsl:if test="..."> instead of if (...)”?) and the execution model surprising (recursive template application by pattern match). For someone who has internalised the model, XSLT 2.0+ is extraordinarily powerful. For someone looking for a quick way to reshape data, it is heavy.

JSON’s answer

There is no direct XSLT equivalent in the JSON ecosystem. jq comes close for command-line data reshaping but is much smaller. JSONata and some template engines approach the use case. For truly document-oriented transformations, XSLT remains the best-in-class option.

Engines

Saxon — the most widely used XSLT 2.0 / 3.0 implementation, Java with a C# port.
libxslt — the de-facto XSLT 1.0 engine, powers most CLI tooling.
Browsers — all major browsers ship XSLT 1.0, usable via XSLTProcessor in JavaScript.

Back to glossary Open JSON tool