What is Meta-ExternalFetcher? Meta's AI crawler

45 of the 389 major websites we measure block Meta-ExternalFetcher in robots.txt (12%), making it number 18 of the 30 AI crawlers we track for how often it is blocked. 35 of those sites name it directly in their robots.txt; the rest are covered by a wildcard rule.

Key facts

What blocking Meta-ExternalFetcher does

Meta says that because of this, the crawler may bypass robots.txt rules.

How to allow or block Meta-ExternalFetcher

Add one of these groups to the robots.txt file at the root of your domain. It is a stated preference that well-behaved crawlers read, not an enforcement mechanism.

User-agent: Meta-ExternalFetcher
Disallow: /

User-agent: Meta-ExternalFetcher
Allow: /

Meta-ExternalFetcher user agent string

The string Meta documents. Version numbers can change, so match on the name.

meta-externalfetcher/1.1

How to verify a request is really Meta-ExternalFetcher

Anyone can put a crawler's name in a user agent string, so the name alone proves nothing. We did not find a published IP list or reverse DNS rule from Meta.

How to whitelist Meta-ExternalFetcher in a firewall or CDN

robots.txt only states a preference. A firewall, CDN or bot protection service can still refuse the request, and the crawler then gets an error even though robots.txt allows it.

1. Check that no group in your robots.txt blocks it, using the rule above.
2. Add an allow rule in your firewall or CDN that matches the name in the user agent. Keep the rule narrow, because anyone can copy a name.
3. Check your server logs for a 200 response from Meta-ExternalFetcher afterwards.

On Cloudflare, also check AI Crawler and Agent access policies, which can block search, agent and training traffic across a site.

Why Meta-ExternalFetcher gets a 403 or 405 error

A 403 means the server refused the request, which usually points to a firewall or bot rule. A 405 means the server refused the request's method, so check any rule that only permits certain methods. A crawler that obeys robots.txt won't request a page it is told to avoid, so an error in your logs points to your server's configuration. To stop it deliberately at the server, this nginx rule returns a 403:

if ($http_user_agent ~* "Meta-ExternalFetcher") {
    return 403;
}

Which sites recently changed their rules for Meta-ExternalFetcher?

See the full change log.

Who blocks Meta-ExternalFetcher, by sector

Sites blocking Meta-ExternalFetcher

academia.edu, amazon.com, arstechnica.com, asahi.com, barrons.com, bloomberg.com, buzzfeednews.com, cntraveler.com, dw.com, flickr.com, ft.com, globeandmail.com, hackernoon.com, huffpost.com, imdb.com, instacart.com, investopedia.com, lifehacker.com, marketwatch.com, mashable.com, metacritic.com, nbcnews.com, netflix.com, newyorker.com, nytimes.com, pcmag.com, pinterest.com, reddit.com, reuters.com, sciencedirect.com, smh.com.au, telegraph.co.uk, theage.com.au, theatlantic.com, theregister.com, thetimes.co.uk, theverge.com, travelandleisure.com, usatoday.com, verywellhealth.com, vox.com, washingtonpost.com, wired.com, wsj.com, zdnet.com.

Sites that allow Meta-ExternalFetcher by name

delta.com, disneyplus.com, hulu.com.

Other Meta crawlers

Meta-ExternalAgent (model training).

See all 30 AI crawlers, the rule change log or the full study. Being reachable is only the first step: how AI search engines choose what to cite covers the rest.

IndexHalo. "Meta-ExternalFetcher block rate across major websites." Measured 3 November 2026. https://www.indexhalo.com/ai-crawlers/meta-externalfetcher/

<a href="https://www.indexhalo.com/ai-crawlers/meta-externalfetcher/">Meta-ExternalFetcher block rate across major websites, IndexHalo</a>