xslt-lab/site/content/xslt/functions/xpath-snapshot.md

title, description, date, version, versionLabel, category, syntax, tags

title	description	date	version	versionLabel	category	syntax	tags
snapshot()	Returns a snapshot copy of the sequence, making streamed nodes available for multiple use.	2026-04-19T00:00:00Z	3.0	XSLT 3.0	node function	snapshot(sequence?)	xslt reference xpath xslt3

Description

snapshot() returns a deep copy of its argument sequence, detached from the original document. Its primary purpose is in streaming mode: when a template is processing a streamed document, nodes are typically available only once and cannot be re-read. Calling snapshot() materializes those nodes into a persistent in-memory copy that can be used multiple times, stored in a variable, or passed to a function that requires grounded (non-streamed) nodes.

Outside of streaming mode, snapshot() behaves identically to copy-of() and produces deep copies of all node items. Atomic values in the sequence are returned unchanged.

When called without arguments in XSLT 3.0, the function snapshots the context item.

Parameters

Parameter	Type	Required	Description
sequence	item()*	No	The sequence to snapshot. Defaults to the context item if omitted.

Return value

item()* — a deep copy of the node items in the sequence; atomic values returned unchanged.

Examples

Capturing streamed nodes for reuse

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<orders>
  <order id="1" amount="100"/>
  <order id="2" amount="200"/>
  <order id="3" amount="150"/>
</orders>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/orders">
    <!-- snapshot() lets us use the orders node-set twice -->
    <xsl:variable name="snap" select="snapshot(order)"/>
    <report>
      <count><xsl:value-of select="count($snap)"/></count>
      <total><xsl:value-of select="sum($snap/@amount)"/></total>
    </report>
  </xsl:template>
</xsl:stylesheet>

Output:

<report>
  <count>3</count>
  <total>450</total>
</report>

Snapshot of the context item

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="order">
    <xsl:variable name="copy" select="snapshot()"/>
    <!-- $copy can be used multiple times -->
    <saved id="{$copy/@id}" amount="{$copy/@amount}"/>
  </xsl:template>

  <xsl:template match="/orders">
    <saved-orders>
      <xsl:apply-templates select="order"/>
    </saved-orders>
  </xsl:template>
</xsl:stylesheet>

Output:

<saved-orders>
  <saved id="1" amount="100"/>
  <saved id="2" amount="200"/>
  <saved id="3" amount="150"/>
</saved-orders>

Notes

• snapshot() is a no-op on atomic values; they are returned unchanged.
• In non-streaming mode, snapshot() and copy-of() produce equivalent results.
• Use snapshot() rather than copy-of() when the intent is specifically to escape the streaming constraint, as this communicates the purpose more clearly to readers.
• The function was added in XPath 3.0 specifically to support the XSLT 3.0 streaming model.

See also

• copy-of()
• accumulator-before()
• accumulator-after()