facebookexternalhit
Facebook external hit web crawler bot
About this crawler
facebookexternalhit is a web crawler identified by the regular-expression pattern facebookexternalhit in the User-Agent request header. It is categorised as social-preview. Use the regex above to detect, log, allow, or block facebookexternalhit traffic in your web server, CDN edge rules, or robots.txt.
Block-rate · top 25k sites
0.65%
Technical details
- Name
- facebookexternalhit
- Pattern
facebookexternalhit- Tags
- social-preview
- Reference
- https://developers.facebook.com/docs/sharing/webmasters/web-crawlers
- Added
- 2012/05/07
- rDNS suffixes
.facebook.com,.fbcdn.net,.fbsv.net,.tfbnw.net- Instances
- 3 known sample(s)
rDNS verification (FCrDNS)
Verify a request is genuinely facebookexternalhit 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.
.facebook.com.fbcdn.net.fbsv.net.tfbnw.net
Sample User-Agent strings
facebookexternalhit/1.0 (+http://www.facebook.com/externalhit_uatext.php)
facebookexternalhit/1.1
facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)
Block this crawler
robots.txt — disallow facebookexternalhit:
User-agent: facebookexternalhit
Disallow: /
Apache .htaccess — return 403:
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} facebookexternalhit [NC]
RewriteRule .* - [F,L]
Nginx — return 403 inside a server block:
if ($http_user_agent ~* "facebookexternalhit") {
return 403;
}
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