Meta-ExternalAgent vs Google-Extended: Which AI Crawler Should You Allow or Block?
Complete side-by-side comparison of Meta-ExternalAgent (Meta) and Google-Extended (Google): user-agent strings, safety ratings, SEO impact, and copy-paste blocking rules. Updated August 2026.
Quick Verdict
Google-Extended has the better safety profile (Safe) compared to Meta-ExternalAgent (Use Caution). If you allow only one, Google-Extended is the lower-risk choice. Meta-ExternalAgent warrants closer monitoring in your server logs, and server-level blocking if robots.txt directives are not respected.
| Attribute | Meta-ExternalAgent | Google-Extended |
|---|---|---|
| Operator | Meta | |
| User-agent string | meta-externalagent |
Google-Extended |
| Category | AI & LLM Bots | AI & LLM Bots |
| Safety rating | Caution | Safe |
| SEO impact if blocked | Varies - Evaluate before blocking | Low - No SEO ranking impact |
| Recommendation | Generally safe to allow; provides legitimate crawling value. | Generally safe to allow; provides legitimate crawling value. |
| Official docs | Meta-ExternalAgent docs | Google-Extended docs |
What is Meta-ExternalAgent?
Meta-ExternalAgent is Meta's crawler for training AI models and improving products, per Meta's crawler documentation. The full profile covers the rest.
What is Google-Extended?
Google-Extended is not a crawler. The full profile covers the rest.
Meta-ExternalAgent vs Google-Extended by the numbers
Meta-ExternalAgent is a training crawler and Google-Extended is an opt-out token rather than a crawler. They do different jobs, so a sensible policy often treats them differently.
| Measure | Meta-ExternalAgent | Google-Extended |
|---|---|---|
| robots.txt token | Meta-ExternalAgent | Google-Extended |
| What it does | collects pages to train AI models | collects pages to train AI models |
| Crawler type | a training crawler | an opt-out token rather than a crawler |
| Priority tier | Tier 1 | Tier 1 |
| Follows robots.txt | Yes, per operator | Not applicable (token) |
| Top-10k robots.txt files | 598 named (10.7%), 706 blocked (12.6%) | 801 named (14.3%), 723 blocked (13%) |
| Blocked by top 1k / middle / tail | 19.2% / 13.4% / 11% | 18.6% / 13.1% / 11.9% |
In our robots.txt study of the Tranco top 10,000 (5,583 valid files, fetched October 20, 2026), Google-Extended is blocked more often than Meta-ExternalAgent: 723 files against 706. The counts are close, which suggests most sites that think about one also think about the other.
Writing rules for both
Because each crawler reads only the group that names it, you can give Meta-ExternalAgent and Google-Extended different answers in the same file. A common pattern, refusing training while allowing search and assistant fetches, looks like this for these two:
User-agent: Meta-ExternalAgent
Disallow: /
User-agent: Google-Extended
Allow: /- One group each. Do not rely on
User-agent: *to cover either crawler if you have named the other; name both. - Copy shared rules. Any
Disallowlines from the*group that should still apply must be repeated in each named group. - Mind the edge. A bot manager can refuse one and admit the other regardless of robots.txt.
- Verify both. The AI crawler access test shows how each is treated on your live site.
Test yourself: if you write User-agent: Meta-ExternalAgent and User-agent: Google-Extended on consecutive lines above one Disallow: /, are both blocked?
Yes. Several User-agent lines in a row form one group, and the rules below apply to every name in it.
Test yourself: does blocking Meta-ExternalAgent also block Google-Extended?
No. Each token is matched separately.
Which to allow, by goal
| Your goal | Meta-ExternalAgent | Google-Extended |
|---|---|---|
| You want AI answers to cite you | Optional | Allow |
| You want to stop AI training | Block | No effect |
| Your server is under load | Rate-limit | Rate-limit |
| You need search traffic | No effect | No effect |
Related: how AI engines choose their sources
Block Meta-ExternalAgent if you do not want your content used for training. Set Google-Extended to control how content is used, not whether it is fetched.
The rest of each operator's family
Meta also runs FacebookBot, facebookexternalhit, Meta-ExternalAds, Meta-ExternalFetcher, meta-externaltest. Rules for Meta-ExternalAgent do not cover them. Google also runs AdsBot-Google, AdsBot-Google-Mobile, APIs-Google, Chrome-Lighthouse, FeedFetcher-Google. Rules for Google-Extended do not cover them.
Read the full profiles for both crawlers, linked in the table above, for documentation links, user-agent strings and server-side rules.
Mistakes when writing rules for Meta-ExternalAgent and Google-Extended together
Meta-ExternalAgent is named in 10.7% of the top-site robots.txt files in our study and blocked in 12.6%; Google-Extended is named in 14.3% of the top-site robots.txt files in our study and blocked in 13%. Large sites block Google-Extended more often, which usually reflects a decision about training rather than about Meta-ExternalAgent.
- They are different kinds of agent (a training crawler versus an opt-out token rather than a crawler), so the usual error is giving them the same rule out of habit. Blocking both to stop training only needs the Meta-ExternalAgent line; the other one changes something else entirely.
- They come from different operators (Meta and Google), with different documentation and different update cycles. Do not assume a change one of them announces applies to the other.
- Putting
User-agent: Meta-ExternalAgentandUser-agent: Google-Extendedin separate groups and then editing only one. Two groups drift apart over time; keep a comment above each that says why it differs from the other.
Each crawler's own profile lists the mistakes that apply to it alone; this list is only about combining the two.
Why Google-Extended never shows up next to Meta-ExternalAgent in your logs
Google-Extended is a control token from Google, not a crawler: nothing with that name ever requests a page. Meta-ExternalAgent is a a training crawler from Meta that does send requests, so it is the only one of the two you can count, verify or rate-limit.
- A firewall rule can act on Meta-ExternalAgent but not on Google-Extended. The token only works as a robots.txt line.
- Blocking Google-Extended does not slow Google's crawling. It changes what Google may do with pages its other crawlers already fetch.
- In our study of top sites, 13% block Google-Extended and 12.6% block Meta-ExternalAgent. Opting out by token is the more common choice here.
How Meta-ExternalAgent and Google-Extended moved in our latest scans
Between our scans of October 17, 2026 and October 20, 2026, files naming Meta-ExternalAgent went from 553 to 598 (+45) and files blocking it from 658 to 706 (+48), so more sites wrote a rule for Meta-ExternalAgent and more of those rules block it. For comparison, 2026 and October 20, 2026, files naming Google-Extended went from 743 to 801 (+58) and files blocking it from 666 to 723 (+57), so more sites wrote a rule for Google-Extended and more of those rules block it.
Over the 3 days between those scans, blocking of Meta-ExternalAgent moved +48 files and blocking of Google-Extended moved +57. Owners are acting faster on Google-Extended, which is the one to recheck first if you have not touched your file this month.
We first recorded Meta-ExternalAgent on March 17, 2026. Meta documents it on developers.facebook.com, and we recheck that page before each release. We first recorded Google-Extended on March 17, 2026. Google documents it on developers.google.com, and we recheck that page before each release.
Related: writing content AI engines can cite
Among the 104 AI and LLM crawlers in our database, Meta-ExternalAgent sits 11th by priority (Tier 1), level with ChatGPT Agent, ChatGPT Operator, ChatGPT-User, ChatGPT-User/2.0. 22 of the 104 share its caution rating. On the Google-Extended side: Among the 104 AI and LLM crawlers in our database, Google-Extended sits eighth by priority (Tier 1), level with ChatGPT Agent, ChatGPT Operator, ChatGPT-User, ChatGPT-User/2.0. 81 of the 104 share its safe rating.
How top sites treat Meta-ExternalAgent and Google-Extended
From our robots.txt study of the Tranco top 10,000 (5,583 valid files, fetched October 20, 2026):
Google-Extended, the most blocked of the Meta-ExternalAgent and Google-Extended tokens: blocked in 13% of files (519 with its own group, 204 throughUser-agent: *), more often by the top 1,000 (18.6%) than the long tail (11.9%).Meta-ExternalAgent, second of the Meta-ExternalAgent and Google-Extended tokens: blocked in 12.6% of files (486 with its own group, 220 throughUser-agent: *), more often by the top 1,000 (19.2%) than the long tail (11%).
For scale, 20.1% of all files block at least one AI training crawler. Google-Extended is one of the tokens driving that figure.
More questions about Meta-ExternalAgent and Google-Extended
- Can I allow one and block the other?
- Yes. Give each its own
User-agentgroup with its own rules. Each crawler reads only the group that names it. - Which of the two visits more often?
- It depends on your site, your audience and how often your content changes. Your access logs are the reliable answer; the commands above count both.
- How long until a change applies?
- Crawlers commonly cache robots.txt for up to a day, so allow about 24 hours and confirm in your logs.
- Do I need to update my rules when either operator launches a new crawler?
- Often, yes. A new token is not covered by rules written for the old ones. Check this comparison and both profiles periodically, or rerun the AI crawlability test after any announcement.
Frequently asked questions
What is the difference between Meta-ExternalAgent and Google-Extended?
Meta-ExternalAgent is operated by Meta (Meta-ExternalAgent is Meta's crawler for training AI models and improving products, per Meta's crawler documentation.) while Google-Extended is operated by Google (Google-Extended is not a crawler. It is a robots.txt token: disallowing it tells Google not to use content crawled by Googlebot for Gemini training and grounding.). They use different user-agent strings (meta-externalagent vs Google-Extended) and must be blocked separately in robots.txt.
Should I block Meta-ExternalAgent or Google-Extended?
Google-Extended has the better safety profile (Safe) compared to Meta-ExternalAgent (Use Caution). If you allow only one, Google-Extended is the lower-risk choice. Meta-ExternalAgent warrants closer monitoring in your server logs, and server-level blocking if robots.txt directives are not respected.
Does blocking Meta-ExternalAgent or Google-Extended hurt SEO?
Meta-ExternalAgent: Varies - Evaluate before blocking. Google-Extended: Low - No SEO ranking impact. Neither is a traditional search-ranking crawler, so blocking them does not affect Google or Bing rankings, but it may reduce your visibility in AI-generated answers.
How do I block both Meta-ExternalAgent and Google-Extended?
Add both user-agent groups to your robots.txt: "User-agent: meta-externalagent" with "Disallow: /" and "User-agent: Google-Extended" with "Disallow: /". Remember robots.txt is voluntary; combine with server-level rules for enforcement.
How to block each bot
Block Meta-ExternalAgent in robots.txt
User-agent: meta-externalagent Disallow: /
Block Google-Extended in robots.txt
User-agent: Google-Extended Disallow: /
Setting Meta-ExternalAgent, Google-Extended and the rest in one go? Tick both in the robots.txt generator (265+ presets), then confirm the result with the AI crawler checker.
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