Child-indexed pseudo-classes matching elements without a parent

Category: CSS
Type: New or changed feature
Status: Enabled by default (Chrome 57)
Intent stage: None

Summary

Change how the child-indexed pseudo-class selectors are matched so they also match elements without a parent. This is a change in the spec from selectors-3 to selectors-4. The reasoning for this is explained in the spec.

Standards & signals

Specification: https://drafts.csswg.org/selectors-4/#child-index
Firefox: Shipped/Shipping
Safari: No signal
Web developers: No signals
Tracking bug: https://bugs.chromium.org/p/chromium/issues/detail?id=675670

Samples: http://software.hixie.ch/utilities/js/live-dom-viewer/?%3C!DOCTYPE%20html%3E%0A%3Cstyle%3Ehtml%20%7B%20color%3A%20red%3B%20%7D%20html%3Afirst-child%20%7B%20color%3A%20green%3B%20%7D%3C%2Fstyle%3E%0Afoo

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