namespace-uri()

Description

namespace-uri() returns the namespace URI part of a node’s expanded name. For an element <xhtml:div xmlns:xhtml="http://www.w3.org/1999/xhtml">, namespace-uri() returns "http://www.w3.org/1999/xhtml".

When called without an argument, it returns the namespace URI of the context node. When called with a node-set, it returns the namespace URI of the first node in document order.

The function returns "" (empty string) for:

• Nodes with no namespace (unprefixed elements in a document without a default namespace, attributes without a prefix).
• Nodes that inherently have no name: text nodes, comment nodes, document nodes.
• The xml: prefix namespace (http://www.w3.org/XML/1998/namespace) is a valid URI that will be returned if the xml: prefix is used.

namespace-uri() is essential for writing namespace-portable stylesheets that identify elements by their canonical URI rather than by the potentially varying prefix used in each source document.

Parameters

Return value

xs:string — the namespace URI of the node, or "" if the node has no namespace.

Examples

Identify elements by namespace URI

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <xhtml:p xmlns:xhtml="http://www.w3.org/1999/xhtml">XHTML paragraph</xhtml:p>
  <p>Plain paragraph</p>
  <svg:rect xmlns:svg="http://www.w3.org/2000/svg" width="100" height="50"/>
</root>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/root">
    <info>
      <xsl:for-each select="*">
        <node name="{local-name()}" ns="{namespace-uri()}"/>
      </xsl:for-each>
    </info>
  </xsl:template>
</xsl:stylesheet>

Output:

<info>
  <node name="p" ns="http://www.w3.org/1999/xhtml"/>
  <node name="p" ns=""/>
  <node name="rect" ns="http://www.w3.org/2000/svg"/>
</info>

Filter elements from a specific namespace

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<doc>
  <html:div xmlns:html="http://www.w3.org/1999/xhtml">Section A</html:div>
  <div>Plain div</div>
  <html:span xmlns:html="http://www.w3.org/1999/xhtml">Span</html:span>
</doc>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/doc">
    <xhtml-only>
      <xsl:for-each select="*[namespace-uri() = 'http://www.w3.org/1999/xhtml']">
        <item><xsl:value-of select="."/></item>
      </xsl:for-each>
    </xhtml-only>
  </xsl:template>
</xsl:stylesheet>

Output:

<xhtml-only>
  <item>Section A</item>
  <item>Span</item>
</xhtml-only>

Notes

• For attributes without a prefix, namespace-uri() returns "" even if they are in scope inside a namespaced element. In XML, unprefixed attributes are not in any namespace.
• The xml: prefix is predeclared and always maps to http://www.w3.org/XML/1998/namespace; namespace-uri() on an xml:lang attribute returns that URI.
• Never rely on name() for namespace-aware matching across documents — always use namespace-uri() and local-name() together.
• In XSLT 2.0+, fn:namespace-uri() is unchanged. The argument must be zero or one node.

See also

• local-name()
• name()