In short. Meta-ExternalAds is Meta's crawler for advertising and other business-related products and services, identified by the meta-externalads user-agent name.

Definition: Meta-ExternalAds is Meta's web crawler for uses that include improving advertising and other business-related products and services. A web crawler is software that fetches content from websites or web applications.

Key facts

As of 17 October 2026, Meta's web crawler documentation assigns Meta-ExternalAds an advertising and business-product purpose.
The IETF's HTTP Semantics standard defines the User-Agent request header and product identifiers containing a name and an optional version.
The IETF's Robots Exclusion Protocol requires case-insensitive matching between a crawler's product token and the relevant robots.txt group.

What crawling does Meta document?

Meta's Meta-ExternalAds description names advertising and other business-related products and services as example uses. The description covers a purpose for fetching website content. It gives site owners a specific crawler name to recognize when reviewing requests associated with those uses.

The same documentation gives Meta-WebIndexer its own section and describes its purpose as improving Meta AI search result quality. These separate names matter when interpreting access logs: a request identifying itself as Meta-ExternalAds belongs under the documented advertising purpose. Meta-WebIndexer is the name associated with search-result improvement.

How does Meta-ExternalAds identify itself?

A user-agent string is the identifying text carried in the User-Agent request header. Meta's published examples show the following strings for Meta-ExternalAds:

meta-externalads/1.1 (+/documentation/sharing/webmasters/web-crawlers)
meta-externalads/1.1

In these examples, meta-externalads is the product name and 1.1 is the version identifier. The longer form adds a documentation reference in parentheses. Searching an access log's user-agent field for meta-externalads therefore covers both published forms.

The User-Agent specification also discusses software masquerading as a different user agent. A matching string records the identity declared in the request; verifying the sender requires evidence beyond that header.

How does robots.txt apply?

A robots.txt file publishes crawling rules for named crawlers and URL paths. Meta's configuration guidance includes a group for meta-externalads that allows general crawling while excluding a directory. The following reproduces its rules with the explanatory comments removed:

User-agent: meta-externalads
Allow: /
Disallow: /private/

The group uses the crawler name without the /1.1 version suffix. The Allow line permits the root path, while the longer Disallow path excludes URLs under /private/.

The Robots Exclusion Protocol's path rules select the most specific match by its length in octets, or bytes. This explains why the directory exclusion takes precedence over the shorter allowance. To request exclusion across the site instead, the group can contain User-agent: meta-externalads followed by Disallow: /.

FAQ

How quickly do robots.txt changes take effect?

Meta's crawler guidance says to allow up to 24 hours because crawlers may cache robots.txt for that period. Account for that interval when reviewing requests after a change.

Can the user-agent string prove that a request comes from Meta?

The HTTP standard describes user agents declaring another agent's identity. Treat the string as a declared software identity when reviewing your logs.

Does a robots.txt exclusion protect confidential pages?

The Robots Exclusion Protocol states that its rules are not access authorization. Protect confidential content with access controls.

Sources

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