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.

Syntax

let customElementRegistry = window.customElements;

Return value

A CustomElementRegistry object instance representing the custom element registry for the current window.

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 Standard
The definition of 'window.customElements' in that specification.
Living Standard Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support54 No1

592

Yes — 593

No4110.1
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support5454 No1

592

Yes — 593

4110.1 ?

1. Under consideration

2. From version 59: this feature is behind the dom.webcomponents.customelements.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

3. 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.

Document Tags and Contributors

Last updated by: lucian95,