facebookexternalhit
Meta · Live retrieval · robots.txt token facebookexternalhit
0.2% of 30,177 measured domains disallow facebookexternalhit in robots.txt at the site root. Separately, and independently of robots.txt, 17.4% of 30,187 reachable domains refuse an AI crawler user agent at the network edge on two consecutive probes from different locations - a refusal the site's own robots.txt does not declare and its owner often has not chosen.
Measured 2026-10-06 by direct request to every domain in the corpus. Method: how this is measured. Reuse under CC BY 4.0 with attribution.
Cite as: Crawl Census, "facebookexternalhit blocking rate", measured 2026-10-06. https://crawlcensus.com/bot/facebookexternalhit
What it is definition
Fetches shared links for Facebook, Instagram and Messenger previews; may bypass robots.txt for integrity checks.
facebookexternalhit is operated by Meta and classified here as live retrieval. These agents fetch a single URL because a user asked about it. Disallowing one means the assistant answers from an older copy or from someone else's summary instead of the live page. Several are documented as not bound by robots.txt, because the request is user-initiated rather than a crawl.
Disallowing facebookexternalhit stops the fetch that happens when a user asks Meta's AI products about one of your URLs. The answer still gets written, from an older copy or from a third party's description of the page, and you no longer control what it says.
- robots.txt token
- facebookexternalhit
- Operator
- Meta
- Purpose
- Live retrieval
- Honors robots.txt
- no
- Documentation
- https://developers.facebook.com/docs/sharing/webmasters/web-crawlers/
Identity on the wire exact string
facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)curl -A 'facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)' https://example.com/Replace the host with your own. A 403, a challenge page or an empty body means the edge is blocking the agent whatever robots.txt says.
How to allow it, how to block it robots.txt
User-agent: facebookexternalhit
Allow: /Absent any rule, the agent is already allowed, so this group only matters when your * group disallows something. Naming the agent replaces the * group for it entirely, so repeat here every disallow you still want to apply to it.
User-agent: facebookexternalhit
Disallow: /Disallowing facebookexternalhit stops the fetch that happens when a user asks Meta's AI products about one of your URLs. The answer still gets written, from an older copy or from a third party's description of the page, and you no longer control what it says.
Sites that block it 60 shown
See every measured domain that blocks facebookexternalhit
This list is served from a cache rebuilt just now. It is discarded the moment a rescan records a policy change for this agent, so a site that has just changed its robots.txt will drop off it within one scan rather than waiting for the cache to expire.
Compare Meta
Meta runs 6 agents in this registry, and they do different jobs. Blocking one says nothing about the others.
Common questions answered
Does blocking facebookexternalhit remove me from Meta's AI products?
Partly. facebookexternalhit fetches a page only when a user asks about it, so disallowing it does not delist you from Meta's AI products. It does mean the answer is composed without your live page, from a stale copy or a third-party summary. Meta documents this agent as not bound by robots.txt, so the disallow is a request rather than a control; see the blocking section for the edge rule that is.
How do I verify facebookexternalhit requests are genuine?
Meta's crawlers originate from AS32934, and Meta documents querying that ASN to obtain the current ranges. Map the source address to its ASN and check for AS32934. There is no published reverse DNS name.
Check your own site free
See whether your robots.txt admits facebookexternalhit today, and whether your edge agrees with it.