CSS @supports : Always non-forgiving parsing

Category: CSS
Type: No developer-visible change
Status: In developer trial (Behind a flag) (Chrome 112)
Intent stage: Prepare to ship

Summary

Some functional selectors are parsed forgivingly. (e.g. :is(), :where()) If an argument of the functional selectors is unknown or invalid, the argument is dropped but the selector itself is not invalidated. To provide a way of detecting the unknown or invalid arguments in those functional selectors, this feature applies the CSS Working Group issue resolution: - @supports uses non-forgiving parsing for all selectors (https://github.com/w3c/csswg-drafts/issues/7280#issuecomment-1143852187)

Standards & signals

Specification: https://drafts.csswg.org/css-conditional-4/#support-definition-ext
Firefox: Shipped/Shipping — https://bugzilla.mozilla.org/show_bug.cgi?id=1789248
Safari: Shipped/Shipping — https://bugs.webkit.org/show_bug.cgi?id=244808
Web developers: Positive — - Thumbs ups in the CSSWG issue: https://github.com/w3c/csswg-drafts/issues/7280 - jQuery applied the spec: https://github.com/jquery/jquery/pull/5107

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