Criticalcss.com
Critical CSS extraction for performance optimization
About this crawler
Criticalcss.com is a web crawler identified by the regular-expression pattern Criticalcss\.com in the User-Agent request header. It is categorised as seo. Use the regex above to detect, log, allow, or block Criticalcss.com traffic in your web server, CDN edge rules, or robots.txt.
Block-rate · top 25k sites
No block-rate data for this crawler.
Technical details
- Name
- Criticalcss.com
- Pattern
Criticalcss\.com- Tags
- seo
- Reference
- https://criticalcss.com/
- Added
- 2026/04/17
- Instances
- 1 known sample(s)
Sample User-Agent strings
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.0 Safari/537.36 Criticalcss.com/2.0.0
Block this crawler
robots.txt — disallow Criticalcss.com:
User-agent: Criticalcss.com
Disallow: /
Apache .htaccess — return 403:
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} Criticalcss\.com [NC]
RewriteRule .* - [F,L]
Nginx — return 403 inside a server block:
if ($http_user_agent ~* "Criticalcss\\.com") {
return 403;
}
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