facebookexternalhit user agent
facebookexternalhit is the user-agent token used by Meta's crawler when it fetches a shared URL to read Open Graph metadata and render a link preview on Facebook and Messenger. It is a preview-generation bot, not a human visit, and is documented in Meta's sharing tooling.
What this means
When a URL is shared on Facebook or Messenger, Meta sends a crawler identified as facebookexternalhit to fetch the page and read its Open Graph tags (og:title, og:image, og:description) to build the link preview.
The preview reflects the metadata the crawler read, not a human page view. Meta provides a Sharing Debugger that triggers a re-scrape, which is why you may see repeated facebookexternalhit fetches of the same URL.
How facebookexternalhit identifies itself
The crawler uses the user-agent token facebookexternalhit. Match on that token rather than a version suffix. Meta documents the token and the Open Graph tags it consumes.
The user agent is a claim like any other and can be copied. The crawler relies on server-rendered Open Graph tags; tags injected only by client-side JavaScript are typically not seen.
- User-agent token: facebookexternalhit
- Reads Open Graph (og:) meta tags
- Meta's Sharing Debugger forces a re-scrape
Debugging a missing preview
If a Facebook preview is blank or stale, run the URL through Meta's Sharing Debugger to see what facebookexternalhit fetched and to refresh the cache. Confirm the page returns 200 with valid og: tags in the initial HTML and is not behind a redirect or login wall.
Finding the facebookexternalhit token in your logs for the shared URL confirms the fetch reached your server.
How it appears in analytics and logs
A request carrying the facebookexternalhit token is Meta fetching a URL to build a share preview. Bursts around a share or a re-scrape are expected bot activity; treat them as crawl events, not visitors.
Diagnostic use case
Confirm whether facebookexternalhit fetched a page after sharing, debug a missing Facebook preview, and keep its requests out of human analytics.
What WebmasterID can help detect
WebmasterID classifies facebookexternalhit server-side as a social-preview bot and shows its fetches on the bot-intelligence view, so preview crawls do not pollute human page-view or referral metrics.
Common mistakes
- Counting facebookexternalhit fetches as human Facebook referral sessions.
- Relying on JavaScript-injected Open Graph tags the crawler does not execute.
- Forgetting Meta caches previews — use the Sharing Debugger to force a re-scrape.
Privacy and accuracy notes
facebookexternalhit detection relies only on the user agent. No person is associated with the fetch — it is an unfurling crawler. WebmasterID records it as a social-preview bot event, separate from human analytics.
Frequently asked questions
- My Facebook preview is outdated — how do I refresh it?
- Use Meta's Sharing Debugger to re-scrape the URL. It re-sends facebookexternalhit and updates the cached Open Graph data Facebook uses for the preview.
Related pages
- Twitterbot user agent
Twitterbot is the crawler operated by X (formerly Twitter) to fetch a shared URL and read its Open Graph and Twitter Card metadata so it can render a preview card in a post. It is a link-unfurling bot, not a human visit, and identifies itself with a documented Twitterbot user-agent token.
- LinkedInBot user agent
LinkedInBot is the crawler LinkedIn uses to fetch a shared URL and read its Open Graph metadata so it can render the link preview attached to a post. It is a preview-generation bot, not a human visit, and identifies itself with a documented LinkedInBot user-agent token plus a self-identifying URL.
- Social preview bot user agents
When someone pastes your link into a social or messaging app, a preview bot fetches the page to build a card from your Open Graph and Twitter Card tags. Bots like facebookexternalhit, Twitterbot, Slackbot, Discordbot, and LinkedInBot identify themselves by token. This page covers what they are and why they hit you.
- Bot intelligence
Server-side classification of preview crawlers and other bots.
Sources and verification notes
- Meta — Sharing webmaster guide (crawler / og: tags)Documents the facebookexternalhit crawler and Open Graph consumption.
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.