::highlight()

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The ::highlight() CSS pseudo-element applies styles to a custom highlight.

A custom highlight is a collection of Range objects and is registered on a webpage using the HighlightRegistry.

Allowable properties

Only certain CSS properties can be used with ::highlight():

color
background-color
text-decoration and its associated properties
text-shadow
-webkit-text-stroke-color, -webkit-text-fill-color and -webkit-text-stroke-width

In particular, background-image is ignored.

Syntax

::highlight(custom-highlight-name)

Examples

Highlighting characters

HTML

<p id="rainbow-text">CSS Custom Highlight API rainbow</p>

CSS

#rainbow-text {
  font-family: monospace;
  font-size: 1.5rem;
}

::highlight(rainbow-color-1) {
  color: #ad26ad;
  text-decoration: underline;
}
::highlight(rainbow-color-2) {
  color: #5d0a99;
  text-decoration: underline;
}
::highlight(rainbow-color-3) {
  color: #0000ff;
  text-decoration: underline;
}
::highlight(rainbow-color-4) {
  color: #07c607;
  text-decoration: underline;
}
::highlight(rainbow-color-5) {
  color: #b3b308;
  text-decoration: underline;
}
::highlight(rainbow-color-6) {
  color: #ffa500;
  text-decoration: underline;
}
::highlight(rainbow-color-7) {
  color: #ff0000;
  text-decoration: underline;
}

JavaScript

const textNode = document.getElementById("rainbow-text").firstChild;

if (!CSS.highlights) {
  textNode.textContent =
    "The CSS Custom Highlight API is not supported in this browser!";
}

// Create and register highlights for each color in the rainbow.
const highlights = [];
for (let i = 0; i < 7; i++) {
  // Create a new highlight for this color.
  const colorHighlight = new Highlight();
  highlights.push(colorHighlight);

  // Register this highlight under a custom name.
  CSS.highlights.set(`rainbow-color-${i + 1}`, colorHighlight);
}

// Iterate over the text, character by character.
for (let i = 0; i < textNode.textContent.length; i++) {
  // Create a new range just for this character.
  const range = new Range();
  range.setStart(textNode, i);
  range.setEnd(textNode, i + 1);

  // Add the range to the next available highlight,
  // looping back to the first one once we've reached the 7th.
  highlights[i % 7].add(range);
}

Result

Specifications

Specification
CSS Custom Highlight API Module Level 1 # custom-highlight-pseudo

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android
`::highlight`	105	105	preview Cannot yet be used with `text-decoration` and `text-shadow`.	91	17.2	105	No Cannot yet be used with `text-decoration` and `text-shadow`.	72	17.2	20.0	105