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 ❌ See webkit.org/b/294895 Vendor position : unknown
Safari on iOS ❌ See webkit.org/b/294895 Vendor position : unknown

Developer signals

State of CSS 2025: reading_list/reading_list question
State of CSS 2025: features/all_features question

Web Platform Tests (WPT)

View the latest WPT test results for this feature

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