The :host CSS pseudo-class selects the shadow host of the shadow DOM containing the CSS it is used inside — in other words, this allows you select a custom element from inside its shadow DOM.

Note: This has no effect when used outside a shadow DOM.

/* Selects a shadow root host */
:host {
  font-weight: bold;




The following snippets are taken from our host-selectors example (see it live also).

In this example we have a simple custom element — <context-span> — that you can wrap around text:

<h1>Host selectors <a href="#"><context-span>example</context-span></a></h1>

Inside the element's constructor, we create style and span elements, fill the span with the content of the custom element, and fill the style element with some CSS rules:

let style = document.createElement('style');
      let span = document.createElement('span');
      span.textContent = this.textContent;

      const shadowRoot = this.attachShadow({mode: 'open'});

      style.textContent = 'span:hover { text-decoration: underline; }' +
                          ':host-context(h1) { font-style: italic; }' +
                          ':host-context(h1):after { content: " - no links in headers!" }' +
                          ':host-context(article, aside) { color: gray; }' +
                          ':host(.footer) { color : red; }' +
                          ':host { background: rgba(0,0,0,0.1); padding: 2px 5px; }';

The :host { background: rgba(0,0,0,0.1); padding: 2px 5px; } rule styles all instances of the <context-span> element (the shadow host in this instance) in the document.


Specification Status Comment
CSS Scoping Module Level 1
The definition of ':host' in that specification.
Working Draft Initial definition.

Browser compatibility

Supported in Chrome and Safari.

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes No1612 3 No Yes Yes
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes No1612 3 Yes Yes Yes

1. Under consideration

2. See bug 1205323

3. From version 61: this feature is behind the dom.webcomponents.shadowdom.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

See also


Document Tags and Contributors

 Contributors to this page: jpmedley, chrisdavidmills
 Last updated by: jpmedley,