CSS :has-slotted support

Description

The :has-slotted CSS pseudo-class matches <slot> elements where the fallback content is not shown. The pseudo-class matches any slotted content, including white space, text nodes, or elements.

For Interop 2027, it would be great to have the :has-slotted selector available across all engines. It has already landed in Firefox. It is being worked on in WebKit (spec clarifications are being sought) and at one point, it was also being worked on in Chromium. Having this cross-engine would remove the need for hacky JS workarounds.

Spec:
https://drafts.csswg.org/css-shadow-1/#the-has-slotted-pseudo

Specification

W3C

web-feature

https://web-platform-dx.github.io/web-features-explorer/features/has-slotted/

Test Links

https://wpt.fyi/results/css?label=master&label=experimental&aligned&q=has-slotted

Additional Signals

• https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Selectors/:has-slotted
• https://groups.google.com/a/chromium.org/g/blink-dev/c/o3ja7zaKuls?pli=1
• https://github.com/w3c/csswg-drafts/issues/14307

Browser positions

• https://github.com/mozilla/standards-positions/issues/1079
• https://github.com/WebKit/standards-positions/issues/404

Start with the CSS Shadow DOM specification section for :has-slotted and review the linked web-features entry and WPT results query. Check the linked browser-position discussions and existing tests returned by the query; done means cross-engine support is tracked against the specification and relevant WPT coverage.