:interest-source CSS pseudo-class

Limited availability

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

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The :interest-source CSS pseudo-class represents an interest invoker element when interest is shown on it.

Syntax

css
:interest-source {
  /* ... */
}

Examples

Selecting an interest invoker element

In this example, we demonstrate how :interest-source can be used to apply styles to an interest invoker element when interest is shown on it.

HTML

The markup includes a <button> and a <p>. We specify the <button> as an interest invoker by giving it the interestfor attribute whose value matches the id of the <p> element, making the paragraph the target element. The paragraph is turned into a popover by giving it the popover attribute, which hides it initially.

html
<button interestfor="mypopover">Button</button>
<p id="mypopover" popover>A hover tooltip</p>

CSS

In the CSS, we specify a rule with an :interest-source selector to apply a specific combination of background-color and color to the <button> when interest is shown on it. We also apply some other styles to the <button>, which are hidden for brevity.

css
button:interest-source {
  background-color: hotpink;
  color: purple;
}

Result

This renders as follows:

Try showing interest in the button (for example, by hovering or focusing it), and note how the hotpink and purple color combination is applied only when interest is shown.

Specifications

Specification
Selectors Level 4
# selectordef-interest-source

Browser compatibility

desktop mobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
interest-source
Experimental
Chrome – Full support
Chrome 142 (Release date: 2025-10-28)
footnote Full support
Edge – Full support
Edge 142 (Release date: 2025-10-31)
footnote Full support
Firefox – No support
Firefox
footnote No support
Opera – Full support
Opera 126 (Release date: 2026-01-08)
footnote Full support
Safari – No support
Safari
footnote No support
Chrome Android – Full support
Chrome Android 142 (Release date: 2025-10-28)
footnote Full support
Firefox for Android – No support
Firefox for Android
footnote No support
Opera Android – Full support
Opera Android 93 (Release date: 2025-11-25)
footnote Full support
Safari on iOS – No support
Safari on iOS
footnote No support
Samsung Internet – No support
Samsung Internet
footnote No support
WebView Android – Full support
WebView Android 142 (Release date: 2025-10-28)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support
Experimental. Expect behavior to change in the future.

See also