AI crawler · Meta · Fetches when a user asks
Meta-ExternalFetcher: what it is, its user agent, and how to block it
Meta-ExternalFetcher is Meta's fetcher for user requests. Fetches individual links a user asks for, including for Meta's agents completing tasks. In our 13 October 2026 study, 184 of 2,332 live top sites with readable robots.txt rules (7.9%) disallow Meta-ExternalFetcher. Part of the AI crawler list.
What Meta-ExternalFetcher does
Operator: Meta. Job: Fetches when a user asks. Partly obeys robots.txt.
“The Meta-ExternalFetcher crawler may bypass robots.txt because it performs fetches that were requested by the user.”
Meta-ExternalFetcher user agent
robots.txt token: Meta-ExternalFetcher (matched case-insensitively).
meta-externalfetcher/1.1 (+/documentation/sharing/webmasters/web-crawlers)meta-externalfetcher/1.1Meta says the string in your logs will be similar to one of these.
robots.txt: allow or block Meta-ExternalFetcher
Allow
User-agent: Meta-ExternalFetcher
Allow: /Block
User-agent: Meta-ExternalFetcher
Disallow: /Affects AI answers and citations. Blocking it refuses the fetch Meta makes when a user asks its assistant to read your page. Meta says robots.txt may not apply to these user-triggered fetches, so a Disallow may change nothing.
Once a group names Meta-ExternalFetcher, it ignores your User-agent: * rules, so copy any paths you still want blocked into it.
How many top sites block Meta-ExternalFetcher
Disallow Meta-ExternalFetcher in robots.txt
7.9%
184 of 2,332 sites
In our 13 October 2026 study, 184 of 2,332 live top sites with readable robots.txt rules (7.9%) disallow Meta-ExternalFetcher.
Sample: Tranco top 5,000, tested once on 13 October 2026 from one Indian fixed-line connection. The robots.txt share counts live sites (home page 2xx) whose rules we could read, as on the AI visibility hub. Method and CSV in the study.
Check your own site
The AI crawler checker reads your robots.txt the way Meta-ExternalFetcher does and tests what your firewall returns. To write the rules, use the AI robots.txt generator.
Check your page: free, about 20 seconds, no sign-in
What it checks
- robots.txt for Meta-ExternalFetcher
- Finds the group Meta-ExternalFetcher obeys under RFC 9309 and the rule that decides your page.
- What your CDN lets through
- Requests the page as OAI-SearchBot, PerplexityBot and Claude-SearchBot and compares the answers with a browser request.
- Content without JavaScript
- AI crawlers don't run JavaScript. The audit checks how much of the page is in the raw HTML.
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Questions
What is Meta-ExternalFetcher?+
Meta-ExternalFetcher is Meta's fetcher for user requests. Fetches individual links a user asks for, including for Meta's agents completing tasks.
What is Meta-ExternalFetcher's user agent?+
Meta documents it as: meta-externalfetcher/1.1 (+/documentation/sharing/webmasters/web-crawlers). Match on the token Meta-ExternalFetcher, since version numbers change.
How do I block Meta-ExternalFetcher?+
Add "User-agent: Meta-ExternalFetcher" followed by "Disallow: /" to your robots.txt. Partly obeys robots.txt, per Meta.
Does blocking Meta-ExternalFetcher affect AI search citations?+
Blocking it refuses the fetch Meta makes when a user asks its assistant to read your page. Meta says robots.txt may not apply to these user-triggered fetches, so a Disallow may change nothing.
How many websites block Meta-ExternalFetcher?+
In our 13 October 2026 study, 184 of 2,332 live top sites with readable robots.txt rules (7.9%) disallow Meta-ExternalFetcher.