::slotted()

The ::slotted() CSS pseudo-element represents any element that has been placed into a slot inside an HTML template (see Using templates and slots for more information).

This only works when used inside CSS placed within a shadow DOM. Note also that this selector won't select a text node placed into a slot; it only targets actual elements.

/* Selects any element placed inside a slot */
::slotted(*) {
  font-weight: bold;
}

/* Selects any <span> placed inside a slot */
::slotted(span) {
  font-weight: bold;
}

::slotted( <compound-selector-list> )where <compound-selector-list> = <compound-selector>#where <compound-selector> = [ <type-selector>? <subclass-selector>* [ <pseudo-element-selector> <pseudo-class-selector>* ]* ]!where <type-selector> = <wq-name> | <ns-prefix>? '*'<subclass-selector> = <id-selector> | <class-selector> | <attribute-selector> | <pseudo-class-selector><pseudo-element-selector> = ':' <pseudo-class-selector><pseudo-class-selector> = ':' <ident-token> | ':' <function-token> <any-value> ')'where <wq-name> = <ns-prefix>? <ident-token><ns-prefix> = [ <ident-token> | '*' ]?  | <id-selector> = <hash-token><class-selector> = '.' <ident-token><attribute-selector> = '[' <wq-name> ']' | '[' <wq-name> <attr-matcher> [ <string-token> | <ident-token> ] <attr-modifier>? ']'where <attr-matcher> = [ '~' |  |  | '^' | '$' | '*' ]? '='<attr-modifier> = i | s

The following snippets are taken from our slotted-pseudo-element demo (see it live also).

In this demo we use a simple template with three slots:

<template id="person-template">
  <div>
    <h2>Personal ID Card</h2>
    <slot name="person-name">NAME MISSING</slot>
    <ul>
      <li><slot name="person-age">AGE MISSING</slot></li>
      <li><slot name="person-occupation">OCCUPATION MISSING</slot></li>
    </ul>
  </div>
</template>

A custom element — <person-details> — is defined like so:

customElements.define('person-details',
  class extends HTMLElement {
    constructor() {
      super();
      let template = document.getElementById('person-template');
      let templateContent = template.content;

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

      let style = document.createElement('style');
      style.textContent = 'div { padding: 10px; border: 1px solid gray; width: 200px; margin: 10px; }' +
                           'h2 { margin: 0 0 10px; }' +
                           'ul { margin: 0; }' +
                           'p { margin: 10px 0; }' +
                           '::slotted(*) { color: gray; font-family: sans-serif; } ';

      shadowRoot.appendChild(style);
      shadowRoot.appendChild(templateContent.cloneNode(true));
  }
})

You'll see that when filling the style element with content, we select all slotted elements (::slotted(*)) and give them a different font and color. This allows them to stand out better next to the slots that haven't been successfully filled.

The element looks like this when inserted into the page:

<person-details>
  <p slot="person-name">Dr. Shazaam</p>
  <span slot="person-age">Immortal</span>
  <span slot="person-occupation">Superhero</span>
</person-details>

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