Cloudflare-Custom-Error-Page-Crawler

monitoring Cloudflare-Custom-Error-Page-Crawler

Custom error page validation and testing

About this crawler

Cloudflare-Custom-Error-Page-Crawler is a web crawler identified by the regular-expression pattern Cloudflare-Custom-Error-Page-Crawler in the User-Agent request header. It is categorised as monitoring. Use the regex above to detect, log, allow, or block Cloudflare-Custom-Error-Page-Crawler 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
Cloudflare-Custom-Error-Page-Crawler
Pattern
Cloudflare-Custom-Error-Page-Crawler
Tags
monitoring
Reference
https://developers.cloudflare.com
Added
2026/04/17
rDNS suffixes
.cloudflare.com
Instances
1 known sample(s)

rDNS verification (FCrDNS)

Verify a request is genuinely Cloudflare-Custom-Error-Page-Crawler with forward-confirmed reverse DNS: the client IP's PTR record must end in one of the suffixes below and a forward A/AAAA lookup of that hostname must return the same IP. UA strings alone are spoofable; FCrDNS is not.

Sample User-Agent strings

Cloudflare-Custom-Error-Page-Crawler

Block this crawler

robots.txt — disallow Cloudflare-Custom-Error-Page-Crawler:

User-agent: Cloudflare-Custom-Error-Page-Crawler Disallow: /

Apache .htaccess — return 403:

RewriteEngine On RewriteCond %{HTTP_USER_AGENT} Cloudflare-Custom-Error-Page-Crawler [NC] RewriteRule .* - [F,L]

Nginx — return 403 inside a server block:

if ($http_user_agent ~* "Cloudflare-Custom-Error-Page-Crawler") { return 403; }
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