Web platform features explorer - sibling-count() and sibling-index()

The sibling-count() and sibling-index() CSS functions return integers that are useful to style elements based on their positions among siblings or on the number of siblings, for example as part of a calc() expression.

Status

Limited availability

MDN documentation

Specifications

CSS Values and Units Module Level 5 (#tree-counting), from Cascading Style Sheets (CSS) Working Group (W3C).

Browser support

Chrome 138 Released on 2025-06-24
Chrome Android 138 Released on 2025-06-24
Edge 138 Released on 2025-06-26
Firefox ❌ See bugzil.la/1953973 Vendor position : positive
Firefox for Android ❌ See bugzil.la/1953973 Vendor position : positive
Safari 26.2 Released on 2025-12-12
Safari on iOS 26.2 Released on 2025-12-12

Baseline availability blocked since December 2025 by Firefox (3 months)

Surveys

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