Web/API/Window/customElements

The customElements read-only property of the Window interface returns a reference to the CustomElementRegistry object, which can be used to register new custom elements and get information about previously registered custom elements.

Examples

The most common example you'll see of this property being used is to get access to the CustomElementRegistry.define() method to define and register a new custom element, e.g.:

let customElementRegistry = window.customElements;
customElementRegistry.define('my-custom-element', MyCustomElement);

However, it is usually shortened to something like the following:

customElements.define('element-details',
  class extends HTMLElement {
    constructor() {
      super();
      const template = document
        .getElementById('element-details-template')
        .content;
      const shadowRoot = this.attachShadow({mode: 'open'})
        .appendChild(template.cloneNode(true));
    }
  }
);

See our web-components-examples repo for more usage examples.

Specification

Specification	Status	Comment
HTML Living StandardThe definition of 'window.customElements' in that specification.	Living Standard	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`customElements`	Chrome Full support 54	Edge Full support 79	Firefox Full support 63 Full support 63 No support 59 — 63 Disabled' Disabled' From version 59 until version 63 (exclusive): this feature is behind the `dom.webcomponents.customelements.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support ? — 59 Disabled' Disabled' Until version 59 (exclusive): this feature is behind the `dom.webcomponents.enabled` preference (needs to be set to `true`) and the `dom.webcomponents.customelements.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera Full support 41	Safari Full support 10.1	WebView Android Full support 54	Chrome Android Full support 54	Firefox Android Full support 63 Full support 63 No support 59 — 63 Disabled' Disabled' From version 59 until version 63 (exclusive): this feature is behind the `dom.webcomponents.customelements.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support ? — 59 Disabled' Disabled' Until version 59 (exclusive): this feature is behind the `dom.webcomponents.enabled` preference (needs to be set to `true`) and the `dom.webcomponents.customelements.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android Full support 41	Safari iOS Full support 10.3	Samsung Internet Android Full support 6.0

Legend

Full support: Full support
No support: No support
User must explicitly enable this feature.': User must explicitly enable this feature.

Window.customElements by Mozilla Contributors is licensed under CC-BY-SA 2.5.