Performance Chat Summary: 23 September 2025

The full chat log is available beginning here on Slack.

Table of Contents

WordPress Performance Trac tickets

@westonruter shared that PR #8412 has tests added and is ready for review, though he still needs to update the description and remove the draft status.
@westonruter enquired about PR #9867, which enables printing script modules in the footer.
- @b1ink0 added that work is currently underway to implement sorting behavior for script modules and their dependencies.
@westonruter enquired about core milestone #63012
regarding theme CSS minification.
- @b1ink0 mentioned having a POC (minification only for block themes) to partially address #63012 and is working with @shyamgadde on a POC addressing the remaining points, with plans to raise PRs in the coming week.
@westonruter mentioned PR #9770 to iterate on fetchpriority for script modules, to allow enqueued script modules to influence the priority of dependencies (or vice versa, which is not yet totally clear).

@westonruter shared that there may be a blocker preventing ticket #63636 from being a good candidate for WordPress 6.9. The issue relates to a bug in Chrome where sending the Clear-Site-Data header such as during logout can slow down page performance. While this approach is preferable to using pageshow to invalidate the bfcache, the Chrome bug may require postponing the feature to 7.0.
@khoipro suggested adding a filter to exclude certain taxonomies from slow term-count queries in large projects.
- @johnbillion noted that while the suggestion didn’t seem directly related, two recent fixes in WordPress 6.9 have already reduced unnecessary term recounting #42522 and #63562.