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.


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:

  class extends HTMLElement {
    constructor() {
      const template = document
      const shadowRoot = this.attachShadow({mode: 'open'})

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


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

Browser compatibility

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