CSSNamespaceRule: namespaceURI property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2018.

The read-only namespaceURI property of the CSSNamespaceRule returns a string containing the text of the URI of the given namespace.

Value

A string containing a URI.

Examples

The stylesheet includes a namespace as the only rule. Therefore the first CSSRule returned will be a CSSNamespaceRule. The value of the namespaceURI property will be http://www.w3.org/1999/xhtml.

css

@namespace url("http://www.w3.org/1999/xhtml");

js
const myRules = document.styleSheets[0].cssRules;
console.log(myRules[0].namespaceURI); // 'http://www.w3.org/1999/xhtml'

Specifications

Specification

CSS Object Model (CSSOM)
# dom-cssnamespacerule-namespaceuri

Browser compatibility

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This page was last modified on Aug 5, 2025 by MDN contributors.

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