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check_circleWP Rocket•error403warningcachecloudcloudflarestylecritical-css•star_halfUncommon•warningModerate

Critical CSS generation blocked by Cloudflare Bot Fight Mode

WP Rocket tries to fetch a URL that generates critical CSS. Cloudflare Bot Fight Mode treats the request as a bot and returns a 403 or 400 response. The plugin receives an empty or error response and stops the generation process.

The request never reaches the generator because Cloudflare blocks the loopback call. The block also triggers timeout errors in WordPress cURL handling. As a result the Critical CSS feature remains inactive.

Symptoms

[dashicons-warning]
WP Rocket error notice
A notice appears in the dashboard stating Critical CSS generation failed with a cURL error 28.
[dashicons-admin-site]
Stalled progress bar
The progress bar in the Critical CSS tab never reaches 100%.
[dashicons-chart-area]
Missing critical CSS in reports
SiteSpeed tools report no critical CSS even though the feature is enabled.
[dashicons-no]
403 responses in network tab
Browser console shows 403 status for URLs like ?wp_rocket_cpcss=1.

Common Causes

Bot Fight Mode blocks generator
Cloudflare identifies the CPCSS request as a bot and returns a challenge response.
IP allow‑list missing
WP Rocket IP range is not whitelisted in firewall or security plugin.
Super Bot Fight Mode mis‑configuration
SBFM is active without the Optimize for WordPress toggle, so loopback requests are challenged.
Additional security layers
Wordfence or similar firewall blocks the same request after Cloudflare challenge.
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