facebookexternalhit is Meta's canonical link-preview crawler. When a URL is shared on Facebook, Instagram, Messenger, or Threads, it fetches the page and reads Open Graph / oEmbed metadata to render the inline preview (title, description, thumbnail). It also covers the older Facebot user-agent and variants like facebookcatalog (commerce surfaces) and facebookplatform.

At a glance

Operator: Meta
Type: Preview

How Centinel checks it

User agent: The request calls itself this crawler. Anyone can send the same string.
IP ranges: The operator publishes the addresses it crawls from, and Centinel checks the client address against that list.

A request that passes one of these checks is facebookexternalhit itself. One that only matches the user agent is reported as unverified. The match tokens, verification domains, and address feeds are not published here.

Allowing or blocking it

The crawler object in the /validate response sets access_allowed to true only for a verified source that your tenant allowlists. A policy rule can allow or block this crawler by its category, Preview.

Back to the crawler catalog