meta-externalfetcher
Meta •
Since 2024
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What is meta-externalfetcher?
meta-externalfetcher is the user agent used when Meta AI products fetch web content in real-time on behalf of users. When users interact with Meta AI across Facebook, Instagram, WhatsApp, or Messenger and request current web information, this bot retrieves the relevant content. It is distinct from both facebookexternalhit (link previews) and FacebookBot (training data). The bot respects robots.txt directives and only fetches content when explicitly triggered by user actions.
User Agent String
meta-externalfetcher
How to Control meta-externalfetcher
Block Completely
To prevent meta-externalfetcher from accessing your entire website, add this to your robots.txt file:
# Block meta-externalfetcher
User-agent: meta-externalfetcher
Disallow: /
Block Specific Directories
To restrict access to certain parts of your site while allowing others:
User-agent: meta-externalfetcher
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: meta-externalfetcher
Crawl-delay: 10
How to Verify meta-externalfetcher
Verification Method:
Verify requests originate from Meta IP ranges
Verify requests originate from Meta IP ranges
Learn more in the official documentation.
⚠️ AI Training Notice
This bot may collect and use your website content for AI model training. Consider whether you want your content used for this purpose before allowing access.
This bot may collect and use your website content for AI model training. Consider whether you want your content used for this purpose before allowing access.
Detection Patterns
Multiple ways to detect meta-externalfetcher in your application:
Basic Pattern
/meta\-externalfetcher/iStrict Pattern
/^meta\-externalfetcher$/Flexible Pattern
/meta\-externalfetcher[\s\/]?[\d\.]*?/iVendor Match
/.*Meta.*meta\-externalfetcher/iImplementation Examples
// PHP Detection for meta-externalfetcher
function detect_meta_externalfetcher() {
$user_agent = $_SERVER['HTTP_USER_AGENT'] ?? '';
$pattern = '/meta\\-externalfetcher/i';
if (preg_match($pattern, $user_agent)) {
// Log the detection
error_log('meta-externalfetcher 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($_SERVER['REQUEST_URI']) . '.html');
exit;
}
return true;
}
return false;
}
# Python/Flask Detection for meta-externalfetcher
import re
from flask import request, make_responsedef detect_meta_externalfetcher():
user_agent = request.headers.get('User-Agent', '')
pattern = r'meta-externalfetcher'
if re.search(pattern, user_agent, re.IGNORECASE):
# Create response with caching
response = make_response()
response.headers['Cache-Control'] = 'public, max-age=3600'
response.headers['X-Robots-Tag'] = 'noarchive'
return True
return False# Django Middleware
class metaexternalfetcherMiddleware:
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
if self.detect_bot(request):
# Handle bot traffic
pass
return self.get_response(request)
// JavaScript/Node.js Detection for meta-externalfetcher
const express = require('express');
const app = express();// Middleware to detect meta-externalfetcher
function detectmetaexternalfetcher(req, res, next) {
const userAgent = req.headers['user-agent'] || '';
const pattern = /meta-externalfetcher/i;
if (pattern.test(userAgent)) {
// Log bot detection
console.log('meta-externalfetcher detected from IP:', req.ip);
// Set cache headers
res.set({
'Cache-Control': 'public, max-age=3600',
'X-Robots-Tag': 'noarchive'
});
// Mark request as bot
req.isBot = true;
req.botName = 'meta-externalfetcher';
}
next();
}app.use(detectmetaexternalfetcher);
# Apache .htaccess rules for meta-externalfetcher# Block completely
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} meta\-externalfetcher [NC]
RewriteRule .* - [F,L]# Or redirect to a static version
RewriteCond %{HTTP_USER_AGENT} meta\-externalfetcher [NC]
RewriteCond %{REQUEST_URI} !^/static/
RewriteRule ^(.*)$ /static/$1 [L]# Or set environment variable for PHP
SetEnvIfNoCase User-Agent "meta\-externalfetcher" is_bot=1# Add cache headers for this bot
<If "%{HTTP_USER_AGENT} =~ /meta\-externalfetcher/i">
Header set Cache-Control "public, max-age=3600"
Header set X-Robots-Tag "noarchive"
</If>
# Nginx configuration for meta-externalfetcher# Map user agent to variable
map $http_user_agent $is_meta_externalfetcher {
default 0;
~*meta\-externalfetcher 1;
}server {
# Block the bot completely
if ($is_meta_externalfetcher) {
return 403;
}
# Or serve cached content
location / {
if ($is_meta_externalfetcher) {
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_meta_externalfetcher) {
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 | Limit Access | Protect pricing and inventory data from AI training |
| Blog/News | Consider Blocking | Your content may be used for AI training without compensation |
| 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: meta-externalfetcher
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: meta-externalfetcher
# Blocking AI training bot
Disallow: /
SaaS/Application Configuration
User-agent: meta-externalfetcher
Disallow: /app/
Disallow: /api/
Disallow: /dashboard/
Disallow: /settings/
Allow: /
Allow: /pricing/
Allow: /features/
Allow: /docs/
Quick Reference
User Agent Match
meta-externalfetcherRobots.txt Name
meta-externalfetcherCategory
aiRespects robots.txt
Yes
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