XSLT Reference
lower-case()
Converts every character of a string to its Unicode lowercase equivalent using locale-independent Unicode case mapping.
Syntax
lower-case(string)Description
lower-case() returns a copy of the input string with every character converted to lowercase according to Unicode default case mappings. The conversion is locale-independent. If the argument is an empty sequence, the function returns the empty string "".
It is the complement of upper-case() and is frequently used for normalization before comparison, sorting, or searching — ensuring that strings like "XML", "xml", and "Xml" are treated identically.
Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
string | xs:string? | Yes | The string to convert. |
Return value
xs:string — the input string with all characters mapped to lowercase.
Examples
Normalizing element text for comparison
Input XML:
<?xml version="1.0" encoding="UTF-8"?>
<tags>
<tag>XSLT</tag>
<tag>XPath</tag>
<tag>xml</tag>
<tag>JSON</tag>
</tags>
Stylesheet:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" indent="yes"/>
<xsl:template match="/tags">
<normalized>
<xsl:for-each select="tag">
<tag><xsl:value-of select="lower-case(.)"/></tag>
</xsl:for-each>
</normalized>
</xsl:template>
</xsl:stylesheet>
Output:
<normalized>
<tag>xslt</tag>
<tag>xpath</tag>
<tag>xml</tag>
<tag>json</tag>
</normalized>
Generating lowercase slugs for URLs
Input XML:
<?xml version="1.0" encoding="UTF-8"?>
<articles>
<article title="Getting Started With XSLT"/>
<article title="Advanced XPath Techniques"/>
</articles>
Stylesheet:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" indent="yes"/>
<xsl:template match="/articles">
<links>
<xsl:for-each select="article">
<xsl:variable name="slug"
select="lower-case(replace(@title, '\s+', '-'))"/>
<a href="/articles/{$slug}"><xsl:value-of select="@title"/></a>
</xsl:for-each>
</links>
</xsl:template>
</xsl:stylesheet>
Output:
<links>
<a href="/articles/getting-started-with-xslt">Getting Started With XSLT</a>
<a href="/articles/advanced-xpath-techniques">Advanced XPath Techniques</a>
</links>
Notes
- Like
upper-case(), this function uses Unicode default case mappings and is not locale-aware. - It does not modify digits, punctuation, or whitespace.
- Combining
lower-case()withnormalize-unicode()is good practice when normalizing data from multiple sources before comparison. - In XSLT 1.0, the nearest equivalent is
translate()with explicit letter-by-letter mapping, which is cumbersome for full Unicode support.