Weston Ruter

This is a temporary workaround for sites experiencing any issues with WordPress 6.9’s new ability to <a href="https://make.wordpress.org/core/2025/11/18/wordpress-6-9-frontend-performance-field-guide/#load-block-styles-on-demand-in-classic-themes" rel="nofollow ugc">load block styles on demand in classic themes</a>, for example <a href="https://core.trac.wordpress.org/ticket/64354" rel="nofollow ugc">#64354</a>.
If running a classic theme (i.e. not a block theme), it filters <code>should_load_separate_core_block_assets</code> to be <code>false</code>. This has the effect of reverting a change introduced in 6.9 where classic themes now load separate core block assets on demand by default.
Note that this plugin should be considered temporary until any issues are resolved in 6.9.1. At any time, you can test whether any issues remain by adding <code>?should_load_separate_core_block_assets=true</code> to any frontend URL; this restores the default behavior in WP 6.9.
This workaround is temporary because there are performance benefits to loading separate core block assets. They can be loaded on demand just when they are used, as opposed to loading the large single combined <code>wp-block-library</code> stylesheet. Loading separate block styles on demand reduces the amount of CSS which should improve page load time.

Load Combined Core Block Assets

Temporary workaround for sites experiencing issues with WordPress 6.9's new ability to load block styles on demand in classic themes.

Brad Jorsch

Andrija Vučinić

Brandon Payton

mreishus

rcrdortiz

This plugin supports a few features that may improve the performance of page loading and rendering in the browser:
<ul>
<li>Concatenate CSS</li>
<li>Concatenate JavaScript</li>
<li>Execution timing of non-critical scripts
<ul>
<li>Note: Changing script execution timing can be risky and will not work well for all sites.</li>
</ul>
</li>
</ul>
<h3>Testing</h3>
To test features without enabling them for the entire site, you may append query params to a WordPress post or page URL. For example, to test enabling JavaScript concatenation for <code>https://example.com/blog/</code>, you can use the URL <code>https://example.com/blog/?concat-js=1</code>.
Supported query params:
<ul>
<li><code>concat-css</code> controls CSS concatenation. Values: <code>1</code> for ON and <code>0</code> for OFF.</li>
<li><code>concat-js</code> controls JavaScript concatenation. Values: <code>1</code> for ON and <code>0</code> for OFF.</li>
<li><code>load-mode-js</code> controls how non-critical JavaScript are loaded. Values: ‘defer’ for <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#attr-defer" rel="nofollow ugc">deferred</a>, ‘async’ for <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#attr-async" rel="nofollow ugc">async loading</a>, any other value indicates the feature should be disabled.</li>
</ul>
<h4>PHPUnit (Docker)</h4>
You can run the PHPUnit tests locally using Docker (no local MySQL required).
First time (or after changing DB credentials):
<pre><code>docker compose down -v
</code></pre>
Run tests:
<pre><code>docker compose up --build --abort-on-container-exit --exit-code-from tests
</code></pre>
Optional overrides (examples):
<ul>
<li><code>WP_VERSION=6.5 docker compose up --build --abort-on-container-exit --exit-code-from tests</code></li>
<li><code>PHP_VERSION=7.4 docker compose up --build --abort-on-container-exit --exit-code-from tests</code></li>
<li><code>PHPUNIT_VERSION=9.6.20 docker compose up --build --abort-on-container-exit --exit-code-from tests</code></li>
</ul>

Page Optimize

Optimize pages for faster load and render in the browser.

Load Combined Core Block Assets vs Page Optimize