facebookexternalhit: user agent, purpose, and whether to allow it
facebookexternalhit generates the link preview card when someone shares your URL. It is not an AI crawler.
Specification
| Operator | Meta |
|---|---|
| Purpose | PreviewGenerates link previews when a URL is shared. Not an AI crawler. Listed because it is frequently mistaken for one in log analysis. |
| Agent kind | FetcherFetches on a person's request. Appears in your logs. Request volume follows human activity. |
| User agent | facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php) |
| robots.txt token | facebookexternalhit |
| robots.txt compliance | Documented non-compliance |
| Verification | No published method, user agent is the only signal |
| Sends referral traffic | Yes |
| Attaches a citation | No |
| Status | Active |
| Legacy Kymo category | other |
| Source | Operator documentationhttps://developers.facebook.com/docs/sharing/webmasters/web-crawlers |
| Verified on |
What blocking it costs you
Blocking it breaks link preview cards on Meta platforms. Meta documents that this crawler might bypass robots.txt when performing security or integrity checks, so a disallow is not guaranteed to stop it. Included here because it is routinely miscounted as AI traffic, which inflates AI crawler numbers.
robots.txt directives
Both blocks below address facebookexternalhit only. Rules for one token never apply to another, even from the same operator.
Allow facebookexternalhit
User-agent: facebookexternalhit Allow: /
Block facebookexternalhit
User-agent: facebookexternalhit Disallow: /
Questions
What is the facebookexternalhit user agent?
facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)
Does facebookexternalhit respect robots.txt?
Documented non-compliance
What does blocking facebookexternalhit cost me?
Blocking it breaks link preview cards on Meta platforms. Meta documents that this crawler might bypass robots.txt when performing security or integrity checks, so a disallow is not guaranteed to stop it. Included here because it is routinely miscounted as AI traffic, which inflates AI crawler numbers.
Related crawlers
All AI crawlers and control tokens
See this bot in your own logs
Kymo classifies every crawler hit server-side using this registry, so facebookexternalhit shows up under Meta with its purpose attached. Read how crawler detection works, or run a free free AI visibility check to see what each crawler currently gets back from your server. No account needed for the check.