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added release notes for tree counting css functions #44610

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e343c1a
added release notes for tree counting css functions
dletorey Jun 30, 2026
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Merge branch 'main' into 44465-tree-counting-ff-release
dletorey Jun 30, 2026
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14 changes: 14 additions & 0 deletions files/en-us/mozilla/firefox/experimental_features/index.md
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Original file line number Diff line number Diff line change
Expand Up @@ -406,6 +406,20 @@ The {{cssxref("@keyframes")}} at-rule now supports [`<timeline-range-name>`](/en
- `layout.css.scroll-driven-animations.enabled`
- : Set to `true` to enable.

### Tree counting CSS functions

The {{cssxref("sibling-count")}} and {{cssxref("sibling-index")}} function are now supported. The `sibling-count()` function returns the number sibling elements as well as the element itself. The `sibling-index()` function returns the index number of the element in relation to its siblings, this starts from `1` and not `0`. ([Firefox bug 2042063](https://bugzil.la/2042063)).

| Release channel | Version added | Enabled by default? |
| ----------------- | ------------- | ------------------- |
| Nightly | 154 | Yes |
| Developer Edition | 153 | No |
| Beta | 153 | No |
| Release | 153 | No |

- `layout.css.tree-counting-functions.enabled`
- : Set to `true` to enable.

## SVG

**No experimental features in this release cycle.**
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5 changes: 5 additions & 0 deletions files/en-us/mozilla/firefox/releases/153/index.md
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Expand Up @@ -104,3 +104,8 @@ Firefox 153 is the current [Beta version of Firefox](https://www.firefox.com/en-
These features are shipping in Firefox 153 but are disabled by default.
To experiment with them, search for the appropriate preference on the `about:config` page and set it to `true`.
You can find more such features on the [Experimental features](/en-US/docs/Mozilla/Firefox/Experimental_features) page.

- **Tree counting CSS functions**: `layout.css.tree-counting-functions.enabled`

The {{cssxref("sibling-count")}} and {{cssxref("sibling-index")}} function are now supported. The `sibling-count()` function returns the number sibling elements as well as the element itself. The `sibling-index()` function returns the index number of the element in relation to its siblings, this starts from `1` and not `0`.
([Firefox bug 2042063](https://bugzil.la/2042063)).