Project Mariner: User Agent, robots.txt Rules & Safety

Q: What user-agent string does Project Mariner use?

Project Mariner is reported to identify itself with GoogleAgent-Mariner. That spelling comes from ai.robots.txt, not from Google, which has not published crawler documentation naming it. Use it in robots.txt as the best available match, and treat a request carrying it as a clue rather than proof of who sent it.

Q: Is Project Mariner safe?

Project Mariner is rated Safe in this directory, meaning there are no credible public reports of abusive crawling under this name. It is a Reported token: Google has not published documentation for it, so its purpose, crawl rate and robots.txt behaviour are not confirmed by the operator, and anyone can send the same user-agent string. Allow or block it on its stated purpose, and back the robots.txt rule with a firewall rule if the traffic matters to you.

Q: Will blocking Project Mariner hurt my SEO?

✅ No SEO Impact - Blocking Project Mariner does not affect your rankings in Google, Bing, or any other search engine. Project Mariner is an AI crawler, not a traditional search indexer. You can freely block it via User-agent / Disallow: / without any SEO penalty.

Q: How do I block Project Mariner in robots.txt?

Add the following lines to your /robots.txt file: User-agent: GoogleAgent-Mariner Disallow: / This instructs Project Mariner not to crawl any path on your site. To block only specific sections, replace / with the path (e.g., Disallow: /blog/).

Q: How do I verify if Project Mariner is crawling my site?

Search your access logs for GoogleAgent-Mariner (for example grep -i "GoogleAgent-Mariner" /var/log/nginx/access.log). Because the operator publishes no IP ranges or reverse-DNS pattern, a match shows that something used the name, not that Google sent it.

Quick Facts

User-Agent:: GoogleAgent-Mariner
Category:: AI & LLM Bots
Operator:: Google
Safety:: Safe
Blocking Impact:: Low - No SEO ranking impact
SEO Impact Score:: 2/10
Official docs:: None published by Google
Named by:: ai.robots.txt

Reported, not operator documented

Google has not published a crawler page that names GoogleAgent-Mariner. It is listed here because a credible public source does: ai.robots.txt. Reported Project Mariner token. Google documents Google-Agent as the fetcher for Mariner.

What that means for you: the robots.txt rule on this page is the best available spelling, and a well-behaved crawler using this string will honour it, but there is no vendor statement of purpose, crawl rate or robots.txt compliance to rely on. Treat a matching request in your logs as a detection clue, not proof of who sent it, and combine the rule with a firewall rule if the traffic matters to you. If the operator publishes documentation, this profile moves to Official docs.

What is Project Mariner?

Project Mariner is an on-demand AI fetcher operated by Google. It retrieves a page only when a user explicitly asks an AI assistant or agent to read, summarize, or act on a specific URL. Because it is triggered by real user intent rather than bulk crawling, blocking it mainly prevents users from pulling your content into Google's assistant.

Project Mariner is an on-demand AI fetcher operated by Google. It retrieves a page only when a user explicitly asks an AI assistant or agent to read, summarize, or act on a specific URL. Because it is triggered by real user intent rather than bulk crawling, blocking it mainly prevents users from pulling your content into Google's assistant.
Project Mariner uses the user-agent token GoogleAgent-Mariner. You can control it via robots.txt, meta tags (noai), or the emerging llms.txt standard. Robots.txt is voluntary; for hard enforcement, combine it with server-level IP blocking.

What happens if you block Project Mariner?

✅ No SEO Impact - Blocking Project Mariner does not affect your rankings in Google, Bing, or any other search engine. Project Mariner is an AI crawler, not a traditional search indexer. You can freely block it via User-agent / Disallow: / without any SEO penalty.

Generally safe to allow; provides legitimate crawling value.

How to block Project Mariner with robots.txt

<code>User-agent: GoogleAgent-Mariner</code> - Matching is case-insensitive. Robots.txt is fetched from the root of each subdomain separately.

Block completely (robots.txt)

User-agent: GoogleAgent-Mariner
Disallow: /

Allow all (robots.txt)

User-agent: GoogleAgent-Mariner
Allow: /

Block private only (robots.txt)

User-agent: GoogleAgent-Mariner
Disallow: /private/
Disallow: /api/
Disallow: /admin/
Allow: /

Nginx server block

# Nginx: Hard-block Project Mariner
if ($http_user_agent ~* "GoogleAgent-Mariner") {
    return 403 "Bot blocked";
}

Apache .htaccess

# Apache: Hard-block Project Mariner
SetEnvIfNoCase User-Agent "GoogleAgent-Mariner" bad_bot
Order Allow,Deny
Allow from all
Deny from env=bad_bot

Meta robots tag

X-Robots-Tag header

X-Robots-Tag: noindex, nofollow

Is Project Mariner safe to allow?

Project Mariner is rated Safe in this directory, meaning there are no credible public reports of abusive crawling under this name. It is a Reported token: Google has not published documentation for it, so its purpose, crawl rate and robots.txt behaviour are not confirmed by the operator, and anyone can send the same user-agent string. Allow or block it on its stated purpose, and back the robots.txt rule with a firewall rule if the traffic matters to you.

Google publishes no IP ranges or reverse-DNS pattern for Project Mariner, so the user-agent string cannot be verified. Rate-limit unusual volume instead of trusting the name.

What does Project Mariner do?

Understanding Project Mariner's purpose helps you decide whether to allow or block it.

Fetches a page only when a user asks an AI assistant to read it
Summarizes or extracts the URL the user provided
Triggered by real user intent, not bulk crawling
Low traffic volume compared with training crawlers
Blocking it prevents users from pulling your content into the assistant

Frequently Asked Questions

What user-agent string does Project Mariner use?

Project Mariner is reported to identify itself with GoogleAgent-Mariner. That spelling comes from ai.robots.txt, not from Google, which has not published crawler documentation naming it. Use it in robots.txt as the best available match, and treat a request carrying it as a clue rather than proof of who sent it.

Is Project Mariner safe?

Project Mariner is rated Safe in this directory, meaning there are no credible public reports of abusive crawling under this name. It is a Reported token: Google has not published documentation for it, so its purpose, crawl rate and robots.txt behaviour are not confirmed by the operator, and anyone can send the same user-agent string. Allow or block it on its stated purpose, and back the robots.txt rule with a firewall rule if the traffic matters to you.

Will blocking Project Mariner hurt my SEO?

✅ No SEO Impact - Blocking Project Mariner does not affect your rankings in Google, Bing, or any other search engine. Project Mariner is an AI crawler, not a traditional search indexer. You can freely block it via User-agent / Disallow: / without any SEO penalty.

How do I block Project Mariner in robots.txt?

Add the following lines to your /robots.txt file:

User-agent: GoogleAgent-Mariner
Disallow: /

This instructs Project Mariner not to crawl any path on your site. To block only specific sections, replace / with the path (e.g., Disallow: /blog/).

Does Project Mariner respect robots.txt?

Not documented. Google has published no statement that Project Mariner reads robots.txt. A rule for GoogleAgent-Mariner will stop a client that chooses to honour it; for enforcement, add a firewall or CDN rule as well.

How do I verify if Project Mariner is crawling my site?

Search your access logs for GoogleAgent-Mariner (for example grep -i "GoogleAgent-Mariner" /var/log/nginx/access.log). Because the operator publishes no IP ranges or reverse-DNS pattern, a match shows that something used the name, not that Google sent it.