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check_circleWP Rocket•codePHPsecurityfirewallstylecritical-csssettingsserver_configurationrocketwp_rocket•star_halfUncommon•warningModerate

Unable to generate Critical CSS – GitHub issue #5891

WP Rocket initiates a request to its remote Critical CSS generator. The request exceeds the PHP execution limit or is blocked by a firewall, causing the process to stop before any CSS is returned.

The generator cannot retrieve the page because of an HTTPS mismatch, a missing title tag, or a service outage. When the request fails, no inline critical CSS is added to the page source.

Symptoms

[dashicons-warning]
Admin notice
Critical CSS generation timed out appears on the Optimize CSS Delivery tab
[dashicons-warning]
Missing inline CSS
No block in the page source
[dashicons-warning]
Regenerate button disabled
Regenerate Critical CSS button stays inactive or returns an error instantly

Common Causes

Server timeout
PHP max execution time or server timeout ends before the generator responds
Outbound request blocked
Firewall, security plugin, or Cloudflare mode prevents the call to critical-css.wp-rocket.me
Generator service outage
External Critical CSS service experiences high load or downtime resulting in delayed responses
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