How to block FacebookExternalHit
Operated by Meta. The primary purpose of FacebookExternalHit is to crawl the content of an app or website that was shared on one of Meta’s family of apps, such as Facebook, Instagram, or Messenger. The link might have been shared by copying and pasting or by using the Facebook social plugin. This crawler gathers, caches, and displays information about the app or website such as its title, description, and thumbnail image.
How it identifies itself
facebookexternalhit/1.0 (+http://www.facebook.com/externalhit_uatext.php)
robots.txt
What the agent asks to be told. It obeys this or it does not — nothing enforces it.
User-agent: facebook Disallow: /
nginx
In the server block, then reload.
# In the server block. 403 rather than 444: a closed connection tells the
# operator nothing, and an agent that gets a status code can log it.
if ($http_user_agent ~* "(facebookexternalhit|facebook|[FBAN)") {
return 403;
}
Apache
In .htaccess or the vhost.
BrowserMatchNoCase "facebookexternalhit" bad_bot
BrowserMatchNoCase "facebook" bad_bot
<RequireAll>
Require all granted
Require not env bad_bot
</RequireAll>
Cloudflare
Security → WAF → Custom rules.
# Security → WAF → Custom rules, action: Block (http.user_agent contains "facebookexternalhit") or (http.user_agent contains "facebook")
WordPress
A child theme's functions.php, or a small plugin.
// functions.php of a child theme, or a small plugin. Runs before WordPress
// builds the page, so a blocked agent costs one PHP process and no queries.
add_action('init', function () {
$agent = $_SERVER['HTTP_USER_AGENT'] ?? '';
foreach (['facebookexternalhit', 'facebook'] as $needle) {
if (stripos($agent, $needle) !== false) {
status_header(403);
exit('Blocked: FacebookExternalHit');
}
}
});
robots.txt is a request. The rules below it are the wall.
FacebookExternalHit publishes a token, so the directive above will work for as long as it keeps honouring it — and nothing except its own good manners makes it. The server rules match on a header the requester sets, which stops the agent that says who it is and not the one that copies somebody else's name. Botscope verifies identity against DNS and published address ranges, records which check decided each request, and shows you the ones that lied.