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

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic supportChrome Full support 54Edge No support No
Notes
No support No
Notes
Notes Under consideration
Firefox Full support 63
Full support 63
No support 59 — 65
Disabled
Disabled From version 59 until version 65 (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 NoOpera Full support 41Safari Full support 10.1WebView Android Full support 54Chrome Android Full support 54Edge Mobile No support No
Notes
No support No
Notes
Notes Under consideration
Firefox Android Full support 63
Full support 63
No support 59 — 65
Disabled
Disabled From version 59 until version 65 (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 41Safari iOS Full support 10.1Samsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

Document Tags and Contributors

Last updated by: newyork-anthonyng,