facebookexternalhit
Meta · reviewed 2026-11-05
About facebookexternalhit
Fetches link previews when users share URLs on Meta apps; not AI training, listed for classification completeness.
Operates Facebook, Instagram and Meta AI; publishes training, ads, fetcher and web-index agents.
Usually means: The vendor has not published enough to say which product triggered the fetch. The hit is real; the intent is not documented.
Identity
User agent
Crawlers are matched by token, not the full browser string. Providers may add version or product text around it.
robots.txt token
Use this token in a User-agent line to allow or block the crawler.
Block this token
User-agent: facebookexternalhit Disallow: /
A Disallow only stops crawlers that honor robots.txt. Classify the category before blocking; check the live file with the robots.txt checker.
Verify a hit
A matching user agent is not proof: any client can send the string. When the vendor publishes network data, compare the request against it before you trust the hit.
Match the user agent
Request UA contains facebookexternalhit.
Check reverse DNS
Hostname ends with fbsv.net.
Check the IP range
Fetch the endpoint below and compare the request IP.
Reverse-DNS suffixes
fbsv.netRange endpoints
A verified hit proves the network path; it does not prove what the crawler will do with the page.
facebookexternalhit: common questions
What is facebookexternalhit?
facebookexternalhit is a crawler from Meta, filed under Other AI bots. Fetches link previews when users share URLs on Meta apps; not AI training, listed for classification completeness. Requests advertise it in the User-Agent header as facebookexternalhit.
Does facebookexternalhit train AI models?
The directory files it under Other AI bots: no training role is documented for it, and the vendor has not published enough to classify it further.
How do I block facebookexternalhit in robots.txt?
Add a group with User-agent: facebookexternalhit and Disallow: / to robots.txt, then re-test the live file. robots.txt matches the token, not the full User-Agent string, and blocking this token does not block the vendor's other crawlers.
How do I verify a facebookexternalhit hit?
Match the user agent, then compare the request IP with the ranges or endpoints listed on this page and check that the hostname ends with fbsv.net. A matching user agent alone is not proof — any client can send the string.
Testing a block? Run the live file through the robots.txt tester or check the whole AI crawler access group.
See when facebookexternalhit hits your site
Page scripts never see AI crawlers because they do not run JavaScript. Install the server probe and each hit lands in the Crawlers block with its path and status.