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/CSS

:host

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 to 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;
}

Syntax

:host {
  /* ... */
}

Examples

Styling the shadow host

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:

const style = document.createElement("style");
const span = document.createElement("span");
span.textContent = this.textContent;

const shadowRoot = this.attachShadow({ mode: "open" });
shadowRoot.appendChild(style);
shadowRoot.appendChild(span);

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.

Specifications

Specification
CSS Scoping Module Level 1 # host-selector

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`:host`	54	79	63	No	41	10	54	54	63	41	10	6.0