Knocklog

FacebookExternalHit

Meta's link preview fetcher.

Operator
Meta
Type
Link preview fetcher
In the user agent
facebookexternalhit
robots.txt token
facebookexternalhit
Follows robots.txt
says it follows robots.txt only in part
Official documentation
developers.facebook.com
Checked on
2026-11-04

What is FacebookExternalHit?

FacebookExternalHit is Meta's link preview fetcher. It loads a page to show its preview when a link is shared in a chat or social network.

The operator's description: Fetches shared links to build previews (title, description, thumbnail). (developers.facebook.com)

How do I block or allow FacebookExternalHit?

With robots.txt, using the token facebookexternalhit. Meta says it follows robots.txt only in part. To block the whole site:

User-agent: facebookexternalhit
Disallow: /

To allow it, use Allow instead of Disallow. Before blocking, weigh what it brings: look at how often it visits and what it brings before deciding.

How do I see whether FacebookExternalHit visits my site?

In your server or CDN access logs, look for facebookexternalhit in the user agent. Google Analytics does not show these visits: agents do not run its JavaScript.

Anyone can copy the name in a user agent, so counting log lines is not enough. Knocklog reads your site's traffic on any host, confirms who is who, and shows how often FacebookExternalHit came, which pages it read and what that brought you.

How do I know it is really FacebookExternalHit?

Meta does not publish a way to verify FacebookExternalHit. Any program can use that name, so Knocklog shows these visits as “unverified”, never as genuine.

Does FacebookExternalHit visit your site?

See in seconds how your site treats AI agents. Then connect your traffic to learn who really came.

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