Re: [csswg-drafts] Is <attr-unit> parse-time behavior intentional? (#13060)

There appears to be enough support to propose an async resolution.

PROPOSED: `attr(foo unknown-unit, fallback) takes the fallback instead of becoming invalid`.

Note that `attr(foo unknown-unit)` (fallback omitted) is already "invalid at computed-value time" per the current spec, via attr()'s [argument grammar](https://drafts.csswg.org/css-values-5/#typedef-attr-args). This proposed resolution does not change this.

cc @tursunova 

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Received on Thursday, 19 March 2026 10:00:16 UTC