fx147 anchor positioning enabled by default

[chrisdavidmills]

Description

Firefox 147 enables CSS anchor positioning by default (https://bugzilla.mozilla.org/show_bug.cgi?id=1988225), and also includes the anchor-center property (https://bugzilla.mozilla.org/show_bug.cgi?id=1909339).

This PR adds appropriate rel notes for these changes, and removes the Experimental features entries for anchor positioning.

There is also another PR related to anchor positioning features added in 147: #42365. We should merge this one first, then update this PR branch and move the note so it fits under the main anchor positioning note. Update: DONE.

Motivation

Additional details

Related issues and pull requests

[github-actions]

Preview URLs

• /en-US/docs/Mozilla/Firefox/Experimental_features
• /en-US/docs/Mozilla/Firefox/Releases/131
• /en-US/docs/Mozilla/Firefox/Releases/147

External URLs (76)

URL: /en-US/docs/Mozilla/Firefox/Experimental_features
Title: Experimental features in Firefox

• https://bugzil.la/1057233 (1 time)
• https://bugzil.la/1099557 (1 time)
• https://bugzil.la/1223880 (1 time)
• https://bugzil.la/1225110 (1 time)
• https://bugzil.la/1280613 (1 time)
• https://bugzil.la/1312588 (1 time)
• https://bugzil.la/1318984 (1 time)
• https://bugzil.la/1391243 (1 time)
• https://bugzil.la/1539075 (1 time)
• https://bugzil.la/1602129 (1 time)
• https://bugzil.la/1617609 (1 time)
• https://bugzil.la/1676779 (1 time)
• https://bugzil.la/1676791 (1 time)
• https://bugzil.la/1687364 (1 time)
• https://bugzil.la/1697647 (1 time)
• https://bugzil.la/1726108 (1 time)
• https://bugzil.la/1736914 (1 time)
• https://bugzil.la/1737918 (1 time)
• https://bugzil.la/1737920 (1 time)
• https://bugzil.la/1744292 (1 time)
• https://bugzil.la/1750902 (1 time)
• https://bugzil.la/1754897 (1 time)
• https://bugzil.la/1794475 (1 time)
• https://bugzil.la/1794628 (1 time)
• https://bugzil.la/1804573 (1 time)
• https://bugzil.la/1807685 (1 time)
• https://bugzil.la/1808410 (1 time)
• https://bugzil.la/1809005 (1 time)
• https://bugzil.la/1817303 (1 time)
• https://bugzil.la/1823463 (1 time)
• https://bugzil.la/1830022 (1 time)
• https://bugzil.la/1853418 (1 time)
• https://bugzil.la/1855763 (1 time)
• https://bugzil.la/1884424 (1 time)
• https://bugzil.la/1884425 (1 time)
• https://bugzil.la/1886134 (1 time)
• https://bugzil.la/1888729 (1 time)
• https://bugzil.la/1889561 (1 time)
• https://bugzil.la/1891446 (1 time)
• https://bugzil.la/1900929 (1 time)
• https://bugzil.la/1921501 (1 time)
• https://bugzil.la/1941406 (1 time)
• https://bugzil.la/1953557 (1 time)
• https://bugzil.la/1954685 (1 time)
• https://bugzil.la/1963263 (1 time)
• https://bugzil.la/1974386 (1 time)
• https://bugzil.la/1976656 (1 time)
• https://bugzil.la/1979915 (1 time)
• https://bugzil.la/1984310 (1 time)
• https://bugzil.la/1991135 (1 time)
• https://bugzil.la/1991688 (1 time)
• https://bugzil.la/1992941 (1 time)
• https://bugzil.la/502258 (1 time)
• https://bugzil.la/558594 (1 time)
• https://bugzil.la/778617 (1 time)
• https://bugzil.la/917755 (1 time)
• https://bugzil.la/918189 (1 time)
• https://bugzilla.mozilla.org (1 time)
• https://developers.google.com/search/docs/specialty/explicit/guidelines (1 time)
• https://drafts.csswg.org/css-inline/ (1 time)
• https://en.wikipedia.org/wiki/Graphics_Processing_Unit (1 time)
• https://github.com/mozilla/explainers/tree/main/archive/ppa-experiment (1 time)
• https://jpeg.org/jpegxl/ (1 time)
• https://support.mozilla.org/en-US/kb/about-config-editor-firefox (1 time)
• https://support.mozilla.org/en-US/kb/privacy-preserving-attribution (1 time)
• https://w3c.github.io/ppa/ (1 time)
• https://wiki.mozilla.org/Origin_Trials (1 time)
• https://www.firefox.com/en-US/ (1 time)
• https://www.firefox.com/en-US/channel/desktop/ (3 times)
• https://www.firefox.com/en-US/channel/desktop/developer/ (2 times)
• https://www.rtalabel.org/?content=howto (1 time)

---

URL: /en-US/docs/Mozilla/Firefox/Releases/131
Title: Firefox 131 release notes for developers

• https://bugzil.la/1838746 (1 time) (Note! This may be a new URL 👀)
• https://bugzil.la/1909358 (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Mozilla/Firefox/Releases/147
Title: Firefox 147 release notes for developers (Beta)

• https://bugzil.la/1909339 (1 time) (Note! This may be a new URL 👀)
• https://bugzil.la/1988225 (1 time) (Note! This may be a new URL 👀)
• https://bugzil.la/1999972 (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2025-12-15 09:28:10)

[bsmth]

TY 👍🏻

[chrisdavidmills]

Thanks @bsmth! I just edited to associate all the anchor positioning rel notes, and thought you might want to have a look.

[bsmth]

Thanks @bsmth! I just edited to associate all the anchor positioning rel notes, and thought you might want to have a look.

Also looking good, tnx 👍🏻