What is facebookexternalhit?

Facebookexternalhit is a web crawler operated by Meta (formerly Facebook) that scans and indexes web content when users share links on Facebook platforms. Created by Facebook's engineering team, this crawler serves as the technical backbone for Facebook's link preview functionality. It identifies itself in server logs with user-agent strings like facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php) or facebookexternalhit/1.0 (+http://www.facebook.com/externalhit_uatext.php). Facebook also uses a related crawler called Facebot for similar purposes.

When someone shares a link on Facebook, Instagram, Messenger, or other Meta platforms, facebookexternalhit visits that URL to gather information about the page content. It analyzes the page's metadata, particularly Open Graph tags, to generate rich previews that include titles, descriptions, and images. This crawler is designed to respect standard web protocols and identifies itself clearly to website owners through its user-agent string.

Meta provides documentation about this crawler through their developer resources, where website owners can learn more about how it operates and how to optimize their content for sharing on Facebook platforms.

Why is facebookexternalhit crawling my site?

Facebookexternalhit crawls your site primarily when users share links to your content on Facebook, Instagram, or other Meta platforms. The crawler visits to collect information needed to generate link previews. These visits are typically triggered by:

A user sharing a link to your website on Facebook or other Meta platforms
Facebook's cache of your page content expiring (Facebook periodically refreshes its cached data)
Someone using Facebook's debugger tools to test how your content appears when shared

The frequency of these visits depends on how often your content is shared on Meta platforms. Popular pages might see multiple visits per day, while less frequently shared content may see the crawler only occasionally.

These crawling activities are considered authorized as they're part of the standard way the web operates, allowing social platforms to generate meaningful previews when users share content.

What is the purpose of facebookexternalhit?

Facebookexternalhit serves to enhance the user experience on Meta platforms by generating rich, informative previews when links are shared. Its primary functions include:

The crawler collects page titles, descriptions, and images to create visually appealing link previews that encourage engagement. This data collection benefits both Meta platforms and website owners: Meta can provide a better user experience with rich content previews, while website owners gain improved visibility and presentation when their content is shared.

For website owners, this crawler provides value by making shared links more attractive and informative, potentially increasing click-through rates from Facebook and other Meta platforms. The crawler is particularly interested in Open Graph (og:) meta tags, which allow website owners to specify exactly how their content should appear when shared.

The data collected is used solely for generating link previews and is not used for advertising targeting or other purposes unrelated to content sharing functionality.

How do I block facebookexternalhit?

While blocking facebookexternalhit is possible, it's generally not recommended as it will negatively impact how your content appears when shared on Facebook, Instagram, and other Meta platforms. If users share links to your site, the previews will be missing images and proper formatting without the crawler's access.

Facebook's crawler respects the robots.txt standard, allowing you to control its access to your site. To block the crawler completely, add the following to your robots.txt file:

User-agent: facebookexternalhit
Disallow: /

To block access to specific directories or pages:

User-agent: facebookexternalhit
Disallow: /private-directory/
Disallow: /confidential-page.html

Alternatively, you can implement server-side detection of the Facebook user agent and return a customized response or HTTP status code. Remember that blocking this crawler will result in poor-quality previews when your content is shared on Meta platforms, potentially reducing click-through rates and engagement. Users may also be less likely to share your content if they see it won't generate attractive previews.

If you're concerned about excessive crawling, consider implementing rate limiting rather than blocking the crawler entirely. This approach allows the crawler to access your content while protecting your server resources.

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