facebookexternalhit
Meta •
Since 2010
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Official Docs
What is facebookexternalhit?
Facebookexternalhit is Meta's crawler that generates link previews when URLs are shared on Facebook, Instagram, and other Meta platforms. The bot reads Open Graph meta tags to create rich previews with titles, descriptions, and images. It's essential for content publishers as these previews significantly impact click-through rates on social media. The crawler also refreshes previews periodically and when explicitly requested through Facebook's Sharing Debugger tool. For websites relying on social media traffic, ensuring facebookexternalhit can properly access and parse their content is crucial for effective social media presence.
User Agent String
facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)
How to Control facebookexternalhit
Block Completely
To prevent facebookexternalhit from accessing your entire website, add this to your robots.txt file:
# Block facebookexternalhit
User-agent: facebookexternalhit
Disallow: /
Block Specific Directories
To restrict access to certain parts of your site while allowing others:
User-agent: facebookexternalhit
Disallow: /admin/
Disallow: /private/
Disallow: /wp-admin/
Allow: /public/
Set Crawl Delay
To slow down the crawl rate (note: not all bots respect this directive):
User-agent: facebookexternalhit
Crawl-delay: 10
How to Verify facebookexternalhit
Verification Method:
Check for Facebook IP ranges or use Facebook's Sharing Debugger
Check for Facebook IP ranges or use Facebook's Sharing Debugger
Learn more in the official documentation.
Detection Patterns
Multiple ways to detect facebookexternalhit in your application:
Basic Pattern
/facebookexternalhit/i
Strict Pattern
/^facebookexternalhit/1\.1 \(\+http\://www\.facebook\.com/externalhit_uatext\.php\)$/
Flexible Pattern
/facebookexternalhit[\s\/]?[\d\.]*?/i
Vendor Match
/.*Meta.*facebookexternalhit/i
Implementation Examples
// PHP Detection for facebookexternalhit
function detect_facebookexternalhit() {
$user_agent = $_SERVER['HTTP_USER_AGENT'] ?? '';
$pattern = '/facebookexternalhit/i';
if (preg_match($pattern, $user_agent)) {
// Log the detection
error_log('facebookexternalhit detected from IP: ' . $_SERVER['REMOTE_ADDR']);
// Set cache headers
header('Cache-Control: public, max-age=3600');
header('X-Robots-Tag: noarchive');
// Optional: Serve cached version
if (file_exists('cache/' . md5($_SERVER['REQUEST_URI']) . '.html')) {
readfile('cache/' . md5($_SERVER['REQUEST_URI']) . '.html');
exit;
}
return true;
}
return false;
}
# Python/Flask Detection for facebookexternalhit
import re
from flask import request, make_response
def detect_facebookexternalhit():
user_agent = request.headers.get('User-Agent', '')
pattern = r'facebookexternalhit'
if re.search(pattern, user_agent, re.IGNORECASE):
# Create response with caching
response = make_response()
response.headers['Cache-Control'] = 'public, max-age=3600'
response.headers['X-Robots-Tag'] = 'noarchive'
return True
return False
# Django Middleware
class facebookexternalhitMiddleware:
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
if self.detect_bot(request):
# Handle bot traffic
pass
return self.get_response(request)
// JavaScript/Node.js Detection for facebookexternalhit
const express = require('express');
const app = express();
// Middleware to detect facebookexternalhit
function detectfacebookexternalhit(req, res, next) {
const userAgent = req.headers['user-agent'] || '';
const pattern = /facebookexternalhit/i;
if (pattern.test(userAgent)) {
// Log bot detection
console.log('facebookexternalhit detected from IP:', req.ip);
// Set cache headers
res.set({
'Cache-Control': 'public, max-age=3600',
'X-Robots-Tag': 'noarchive'
});
// Mark request as bot
req.isBot = true;
req.botName = 'facebookexternalhit';
}
next();
}
app.use(detectfacebookexternalhit);
# Apache .htaccess rules for facebookexternalhit
# Block completely
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} facebookexternalhit [NC]
RewriteRule .* - [F,L]
# Or redirect to a static version
RewriteCond %{HTTP_USER_AGENT} facebookexternalhit [NC]
RewriteCond %{REQUEST_URI} !^/static/
RewriteRule ^(.*)$ /static/$1 [L]
# Or set environment variable for PHP
SetEnvIfNoCase User-Agent "facebookexternalhit" is_bot=1
# Add cache headers for this bot
<If "%{HTTP_USER_AGENT} =~ /facebookexternalhit/i">
Header set Cache-Control "public, max-age=3600"
Header set X-Robots-Tag "noarchive"
</If>
# Nginx configuration for facebookexternalhit
# Map user agent to variable
map $http_user_agent $is_facebookexternalhit {
default 0;
~*facebookexternalhit 1;
}
server {
# Block the bot completely
if ($is_facebookexternalhit) {
return 403;
}
# Or serve cached content
location / {
if ($is_facebookexternalhit) {
root /var/www/cached;
try_files $uri $uri.html $uri/index.html @backend;
}
try_files $uri @backend;
}
# Add headers for bot requests
location @backend {
if ($is_facebookexternalhit) {
add_header Cache-Control "public, max-age=3600";
add_header X-Robots-Tag "noarchive";
}
proxy_pass http://backend;
}
}
Should You Block This Bot?
Recommendations based on your website type:
| Site Type | Recommendation | Reasoning |
|---|---|---|
| E-commerce | Optional | Evaluate based on bandwidth usage vs. benefits |
| Blog/News | Allow | Increases content reach and discoverability |
| SaaS Application | Block | No benefit for application interfaces; preserve resources |
| Documentation | Selective | Allow for public docs, block for internal docs |
| Corporate Site | Limit | Allow for public pages, block sensitive areas like intranets |
Advanced robots.txt Configurations
E-commerce Site Configuration
User-agent: facebookexternalhit
Crawl-delay: 5
Disallow: /cart/
Disallow: /checkout/
Disallow: /my-account/
Disallow: /api/
Disallow: /*?sort=
Disallow: /*?filter=
Disallow: /*&page=
Allow: /products/
Allow: /categories/
Sitemap: https://example.com/sitemap.xml
Publishing/Blog Configuration
User-agent: facebookexternalhit
Crawl-delay: 10
Disallow: /wp-admin/
Disallow: /drafts/
Disallow: /preview/
Disallow: /*?replytocom=
Allow: /
SaaS/Application Configuration
User-agent: facebookexternalhit
Disallow: /app/
Disallow: /api/
Disallow: /dashboard/
Disallow: /settings/
Allow: /
Allow: /pricing/
Allow: /features/
Allow: /docs/
Quick Reference
User Agent Match
facebookexternalhit
Robots.txt Name
facebookexternalhit
Category
social
Respects robots.txt
Yes
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