is

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The is global attribute allows you to specify that a standard HTML element should behave like a defined custom built-in element (see Using custom elements for more details).

This attribute can only be used if the specified custom element name has been successfully defined in the current document, and extends the element type it is being applied to.

Examples

The following code is taken from our word-count-web-component example (see it live also).

js
// Create a class for the element
class WordCount extends HTMLParagraphElement {
  constructor() {
    // Always call super first in constructor
    super();

    // Constructor contents omitted for brevity
    // …
  }
}

// Define the new element
customElements.define("word-count", WordCount, { extends: "p" });
html
<p is="word-count"></p>

Specifications

Specification
HTML
# attr-is

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
is

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support
See implementation notes.

See also