nuclei
ProjectDiscovery fast customizable vulnerability scanner
About this crawler
nuclei is a web crawler identified by the regular-expression pattern nuclei in the User-Agent request header. It is categorised as scanner. Use the regex above to detect, log, allow, or block nuclei traffic in your web server, CDN edge rules, or robots.txt.
Block-rate · top 25k sites
0.46%
Technical details
- Name
- nuclei
- Pattern
nuclei- Tags
- scanner
- Reference
- https://docs.projectdiscovery.io/opensource/nuclei/running
- Added
- 2026/05/02
- rDNS suffixes
.projectdiscovery.io- Instances
- 1 known sample(s)
rDNS verification (FCrDNS)
Verify a request is genuinely nuclei 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.
.projectdiscovery.io
Sample User-Agent strings
Mozilla/5.0 (Windows NT 10.0; WOW64) / nuclei
Block this crawler
robots.txt — disallow nuclei:
User-agent: nuclei
Disallow: /
Apache .htaccess — return 403:
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} nuclei [NC]
RewriteRule .* - [F,L]
Nginx — return 403 inside a server block:
if ($http_user_agent ~* "nuclei") {
return 403;
}
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