What it does
meta-externalfetcher is Meta's user action crawler. A live fetch made because a human asked the assistant about your page right now. Closest thing to a real visitor; several of these (Perplexity-User, meta-externalfetcher) ignore robots.txt by design because the request is user-initiated.
User-initiated link fetches; Meta's docs now frame it as fetching individual links at a user's request to support 'evaluating and improving agentic AI capabilities', and state it may bypass robots.txt because a user requested the fetch. Doc re-verified live 2026-08-22.
Full UA: not captured in our July 2026 roster review — match log hits on the token meta-externalfetcher (case-insensitive substring) and verify by IP before acting.
How to verify a hit is really meta-externalfetcher
Verification method (July 2026): Meta ASN 32934 (RDAP/whois); docs page fetched live 2026-08-22
No per-crawler IP list is published; the practical check is network ownership — look up the hit's source IP via RDAP/whois and confirm it announces from the vendor's network (ASN) rather than a residential proxy or cloud range.
User-agent strings are freely spoofed, so a UA match alone proves nothing. Full step-by-step method: verify by IP.
Allow or block in robots.txt
Match the exact token meta-externalfetcher in robots.txt:
# Block meta-externalfetcher site-wide
User-agent: meta-externalfetcher
Disallow: /# Explicitly allow meta-externalfetcher
User-agent: meta-externalfetcher
Allow: /For the allow-search-block-training combined pattern (and the Allow-directive gotcha that silently kills carve-outs), see the robots.txt guide. robots.txt governs whether meta-externalfetcher may fetch; llms.txt is the separate, curated map AI assistants read once allowed in.
Vendor documentation: https://developers.facebook.com/docs/sharing/webmasters/web-crawlers
The Meta family
Meta operates 4 distinct tokens in this roster, and they do not block each other: a robots.txt line for meta-externalfetcher does nothing to its siblings — each needs its own User-agent: entry (the robots.txt guide has combined patterns).
| Token | Role | robots.txt |
|---|---|---|
| meta-externalagent | Training | claims robots compliance |
| meta-webindexer | AI search | claims robots compliance |
| meta-externalads | Training | claims robots compliance |
Frequently asked questions
What is meta-externalfetcher?
meta-externalfetcher is Meta's user action crawler. A live fetch made because a human asked the assistant about your page right now. Closest thing to a real visitor; several of these (Perplexity-User, meta-externalfetcher) ignore robots.txt by design because the request is user-initiated.
Does meta-externalfetcher respect robots.txt?
No — meta-externalfetcher does not treat robots.txt as binding. Blocking it requires WAF or IP-level rules.
How do I block meta-externalfetcher?
robots.txt cannot stop meta-externalfetcher; block it with WAF or IP-level firewall rules instead.
How do I verify meta-externalfetcher traffic by IP?
No per-crawler IP list is published; look up the source IP via RDAP/whois and confirm it announces from Meta's network before trusting the user agent.
Related bots
Same vendor, then other user-action fetchers — the full directory profiles all 34.