This GitHub issue is for collecting web developer signals for 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.

Browser support

• Chrome 138 (Jun 24, 2025)
• Chrome Android 138 (Jun 24, 2025)
• Edge 138 (Jun 26, 2025)
• Firefox: not supported
• Firefox for Android: not supported
• Safari 26.2 (Dec 12, 2025)
• Safari on iOS 26.2 (Dec 12, 2025)

Give us feedback

If you're pressed for time, but you want this feature to be available in all browsers, please give this issue a thumbs up 👍 reaction.

However, a much better guide for us is to know how you'd use this feature, and what you're having to do in the meantime. This helps us judge the priority versus other features.

Copy the template below in a comment, and add the details that matter to you.

## What I want to do with this feature

<!-- Add your specific use-cases, even if they seem obvious to you. -->

## What I'm having to do in the meantime

<!--
Are you having to use another feature instead, a polyfill, or is it blocking you completely?
Why are the alternatives worse than using this feature?
-->

All comments are expected to adhere to the Code of Conduct.

Learn more

You can learn more about this feature here:

• web features explorer
• webstatus.dev
• Specification