Published on 2025-08-07T06:18:08Z

facebookexternalhit

facebookexternalhit is the official web crawler for Meta (formerly Facebook). Its purpose is to fetch and scan web pages when users share links on Facebook, Instagram, Messenger, and other Meta platforms. The bot analyzes metadata, particularly Open Graph tags, to generate the rich visual previews (including titles, descriptions, and images) that appear alongside shared links. This improves user experience and can increase click-through rates for website owners.

What is facebookexternalhit?

facebookexternalhit is a web crawler operated by Meta (formerly Facebook) that is essential for the platform's link preview functionality. When a user shares a link on a Meta platform like Facebook or Instagram, this crawler visits the URL to gather metadata. It identifies itself in server logs with user-agent strings such as facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php). The bot primarily looks for Open Graph (og:) meta tags to generate rich previews that include a title, description, and image. Meta provides detailed documentation for webmasters on how to optimize their sites for this crawler.

Why is facebookexternalhit crawling my site?

The facebookexternalhit crawler is visiting your site because a user has shared a link to your content on a Meta platform. Its visit is triggered by this sharing action, not by a regular crawling schedule. The bot is collecting the necessary information to create a link preview. The frequency of visits is directly proportional to how often your content is shared on Facebook, Instagram, or other Meta services. This is a standard and authorized part of how social media platforms handle external links.

What is the purpose of facebookexternalhit?

The primary purpose of facebookexternalhit is to enhance the user experience on Meta platforms by generating rich, informative previews for shared links. By collecting metadata, the crawler creates visually appealing preview cards that encourage user engagement. This benefits both Meta, by providing a better user experience, and website owners, who gain better visibility and presentation when their content is shared. For website owners, optimizing Open Graph tags is key to controlling how content appears in these previews, which can lead to higher click-through rates from Meta's platforms.

How do I block facebookexternalhit?

If you wish to prevent Meta from creating link previews for your site, you can block the facebookexternalhit crawler. Note that this will cause links to your site to appear as plain text URLs without any preview. You can add the following rule to your robots.txt file.

To block this bot, use this directive:

User-agent: facebookexternalhit
Disallow: /

How to verify the authenticity of the user-agent operated by Meta?

Reverse IP lookup technique

To verify user-agent authenticity, you can use host linux command two times with the IP address of the requester.

```
> host IPAddressOfRequest
```
This command returns the reverse lookup hostname (e.g., 4.4.8.8.in-addr.arpa.).

> host ReverseDNSFromTheOutputOfFirstRequest

If the output matches the original IP address and the domain is associated with a trusted operator (e.g., Meta), the user-agent can be considered legitimate.

IP list lookup technique

Some operators provide a public list of IP addresses used by their crawlers. This list can be cross-referenced to verify a user-agent's authenticity. However, both operators and website owners may find it challenging to maintain an up-to-date list, so use this method with caution and in conjunction with other verification techniques.