JavaScript Element namespaceURI Property
Definition
Element.namespaceURI is a read-only property that returns the element’s namespace URI as a string, or null if it is not in a namespace (MDN).
Read the notes below before you get or set this property. Prefer feature detection when support is limited.
Syntax
Use el.namespaceURI. Start with this line.
| Call | What it does |
|---|
element.namespaceURI | Primary signature. |
Built into the browser. Read or assign el.namespaceURI — no import required.
Library declarations
Parameters
| Parameter | Description |
|---|
| localName | Optional. Often checked together with the URI |
Return Value
| Return Value | Description |
|---|
| * | String or null |
JavaScript Examples
Example 1 — HTML namespaceURI
Read the namespace of a normal HTML element.
const box = document.getElementById("box");
console.log(box.namespaceURI);
// "http://www.w3.org/1999/xhtml"
http://www.w3.org/1999/xhtml
How It Works
- Find an HTML element. A
<div> in an HTML document. - Read
namespaceURI. You get the XHTML namespace string. - MDN note. HTML elements in HTML docs use the same URI as XHTML.
- Read-only. The value was set when the node was created.
Example 2 — SVG with createElementNS
Create a real SVG circle in the SVG namespace.
const SVG_NS = "http://www.w3.org/2000/svg";
const circle = document.createElementNS(SVG_NS, "circle");
console.log(circle.namespaceURI);
// "http://www.w3.org/2000/svg"
console.log(circle.localName);
// "circle"
http://www.w3.org/2000/svg
circle
How It Works
- Pick the SVG URI. Store it in a constant for clarity.
- Create with
createElementNS. The namespace is set at creation. - Read it back.
namespaceURI matches the SVG URI. localName is separate. Here it is "circle".
Example 3 — Check Namespace + Local Name
Confirm both the URI and the local name (MDN-style check).
const SVG_NS = "http://www.w3.org/2000/svg";
const el = document.createElementNS(SVG_NS, "circle");
const isSvgCircle =
el.localName === "circle" &&
el.namespaceURI === SVG_NS;
console.log(isSvgCircle); // true
How It Works
- Same local name can exist in different namespaces. Name alone is not enough.
- Check
localName. Here it must be "circle". - Check
namespaceURI. It must be the SVG URI. - Both true → you have a real SVG circle element.
Compatibility
Browser Support
Element.namespaceURI is Baseline Widely available (MDN: since July 2015). Safe across modern and older evergreen browsers.
✓ Baseline · Widely available
Element.namespaceURI
Read-only namespace URI string or null — frozen at element creation time.
Google Chrome All versions · Desktop & Mobile
Full support
Mozilla Firefox All versions · Desktop & Mobile
Full support
Apple Safari All versions · macOS & iOS
Full support
Microsoft Edge All versions · Chromium & Legacy
Full support
Internet Explorer IE 6+ · Legacy environments
Full support
Opera All modern versions
Full supportnamespaceURI Excellent
Bottom line: Safe for production. Use createElementNS when you need SVG or other namespaces.
Frequently Asked Questions
The namespace URI of the element as a string, or null if the element is not in a namespace.
No. MDN marks Element.namespaceURI as Baseline Widely available (since July 2015). It is not Deprecated, Experimental, or Non-standard.
In HTML documents, HTML elements use http://www.w3.org/1999/xhtml (the same namespace as XHTML).
Use document.createElementNS(namespaceURI, qualifiedName). For SVG, use http://www.w3.org/2000/svg.
No. MDN notes the namespace URI is frozen at node creation time — it is not recomputed from later namespace declarations.
localName is the local tag name (for example circle). namespaceURI is which namespace that name belongs to. You often check both together.
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