Safe Reported AI & LLM Bots

Project Mariner

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

Project Mariner is reported to identify itself with GoogleAgent-Mariner . Evidence that the spelling is in real use comes from our own robots.txt study: 69 of the 5,583 valid robots.txt files in the Tranco top 10,000 name it (fetched October 20, 2026), 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.

Operated by Google

Scout's quick take

Project Mariner visits a page only when a person asks Google's assistant to open it. It is not a background crawler. This profile is built from reported sightings, not vendor documentation.

# Block only if you really mean to
User-agent: GoogleAgent-Mariner
Disallow: /

Check if ChatGPT can read my site Build a full robots.txt

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
Evidence:: Verified by AI Crawler Check: in 69 top-10k robots.txt files

Reported, not operator documented

Google has not published a crawler page that names GoogleAgent-Mariner. It is listed here on our own evidence. Verified by AI Crawler Check: 69 of the 5,583 valid robots.txt files in the Tranco top 10,000 carry a rule for GoogleAgent-Mariner, so site owners treat it as a real crawler name (how we measure this). That proves the spelling is in use, not who sends it. Reported Project Mariner token. Google documents Google-Agent as the fetcher for Mariner.

What that means for you: the GoogleAgent-Mariner rule on this page is the best available spelling, but Google has made no statement of purpose, crawl rate or robots.txt compliance. Treat a GoogleAgent-Mariner request in your logs as a clue, not proof of who sent it, and add a firewall rule if that 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 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.

Want to see whether Project Mariner actually visits you? Read how do I monitor AI bot traffic to my website?

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

Project Mariner in context

Project Mariner is a user-triggered agent operated by Google. In plain terms, it fetches a page when a person asks an assistant or app to open it. Our database files it under AI and LLM crawlers and ranks it Tier 2, important crawlers from established AI and search operators. 74 of the 104 AI and LLM crawlers in our database share this tier.

Its safety rating is safe and its blocking impact is low. So the decision about Project Mariner rests on what you want from Google, not on its behaviour. How we rate safety and impact.

How site owners treat Project Mariner

In our own scan of the Tranco top 10,000 (5,583 valid robots.txt files), 69 files (1.2%) name GoogleAgent-Mariner in a User-agent line. That shows site owners treat the token as a real crawler worth a rule. It does not, on its own, prove who operates it.

Does it follow robots.txt?

Project Mariner's operator does not clearly document how it treats robots.txt. Write the Project Mariner rule anyway, then confirm in your logs that its requests stop.

Google crawlers and close alternatives

Project Mariner is one of 32 Google crawlers in our database. A User-agent: GoogleAgent-Mariner group controls Project Mariner only; the other Google tokens below need their own lines.

GoogleAgent-Mariner: this crawler (Tier 2)
AdsBot-Google: Google Ads Quality (Desktop), checks pages for an SEO, uptime or analytics service (Tier 3)
AdsBot-Google-Mobile: Google Ads Quality (Mobile), checks pages for an SEO, uptime or analytics service (Tier 3)
APIs-Google: APIs-Google, fetches a page when a person asks an assistant or app to open it (Tier 3)
Chrome-Lighthouse: Lighthouse Audit, checks pages for an SEO, uptime or analytics service (Tier 4)
FeedFetcher-Google: Google Feed Fetcher, builds a search or answer index (Tier 3)
Gemini-Deep-Research: Gemini-Deep-Research, fetches a page when a person asks an assistant or app to open it (Tier 3)
Google-Agent: Google Agent (Project Mariner), fetches a page when a person asks an assistant or app to open it (Tier 2)
Google-CloudVertexBot: Google Vertex AI, fetches a page when a person asks an assistant or app to open it (Tier 3)

To give Project Mariner the same answer as its siblings, stack User-agent: GoogleAgent-Mariner with their lines above one set of rules; to treat Project Mariner differently, give it its own group.

Other AI and LLM crawlers that do the same job (fetches a page when a person asks an assistant or app to open it) include ChatGPT Agent from OpenAI, ChatGPT Operator from OpenAI, ChatGPT-User from OpenAI, ChatGPT-User/2.0 from OpenAI, Claude-SearchBot from Anthropic, Claude-User from Anthropic. Deciding about Project Mariner is usually a decision about the whole group, so check how your file treats these too.

We first recorded GoogleAgent-Mariner on June 18, 2026. We could not find a page where Google names it, so treat the token as reported rather than documented.

Which rule Project Mariner actually follows

Project Mariner reads exactly one group in robots.txt, the most specific one that names GoogleAgent-Mariner, and never combines rules across groups. This short file shows the trap:

User-agent: *
Disallow: /private/

User-agent: GoogleAgent-Mariner
Disallow: /drafts/

Find the group. Project Mariner looks for a group naming GoogleAgent-Mariner. One exists, so it ignores User-agent: * completely.
Apply only that group. It is refused /drafts/ and nothing else.
The surprise. /private/ is open to Project Mariner, because that rule lives in the * group it no longer reads. To keep it out of both, repeat Disallow: /private/ inside its own group.

Test yourself: does a rule under User-agent: * apply to Project Mariner if the file also has a User-agent: GoogleAgent-Mariner group?

No. Once a group names it, Project Mariner reads only that group. Put every rule you want it to follow inside its own group.

Test yourself: will blocking Project Mariner remove your pages from AI answers?

Often, yes. Project Mariner is a user-triggered agent, so pages it cannot fetch can drop out of the answers or results it supports.

Test yourself: is User-agent: googleagent-mariner the same as User-agent: GoogleAgent-Mariner?

Yes. RFC 9309 makes user-agent matching case-insensitive. Paths are a different story: Disallow: /Blog/ does not block /blog/.

Should you allow Project Mariner? Decide by situation

Recommended setting for Project Mariner by type of site
If you are...	Recommended setting
You publish content and want AI answers to cite it	Allow it. Project Mariner fetches pages for answers, so blocking it can remove you from them.
You license content and want to stop AI training	Blocking it does not stop training, because Project Mariner is a user-triggered agent. Block the operator's training crawler instead.
You run an online shop	Allow it on product and category pages, which are the pages shoppers ask assistants about.
Your server is under load from bots	Rate-limit before blocking. It is rated safe in our database.

Check Project Mariner on your own site

Open /robots.txt on your domain and search for GoogleAgent-Mariner. If it is not named, it follows User-agent: *.
List the Disallow lines in the group Project Mariner follows and test your key URLs against them; the longest match wins, and Allow wins a tie.
Look beyond the file. A firewall or bot manager can refuse Project Mariner even when robots.txt allows it, and that never shows in the file.
Run our free AI crawler check to see how Project Mariner and every other crawler we track are treated in one pass, including firewall refusals.

Common mistakes with Project Mariner

The errors we see most often with Project Mariner in the files and firewalls we test:

Assuming a robots.txt rule will stop Project Mariner. User-triggered fetches act for a person, and some operators say robots.txt may not apply to them. Check the operator's statement above.
Blocking Project Mariner as if it were a bulk crawler. It fetches one page because a person asked; blocking it means that person's assistant cannot read your page.
Counting Project Mariner visits as crawl volume. Each request maps to a real user question, which makes the paths it requests a useful signal of what people ask about you.

All three hide inside a file that looks correct, so check Project Mariner from outside after every change.

Spotting Project Mariner in your logs

robots.txt says what Project Mariner may do; your access logs show what it actually did.

Count requests

On a server with standard Nginx or Apache logs, this counts matching requests per day (adjust the log path for your host):

grep -iE "GoogleAgent-Mariner" /var/log/nginx/access.log \
  | awk '{print $4}' | cut -d: -f1 | sort | uniq -c

And this shows which paths it requested most, which is the quickest way to see whether your Disallow lines are being respected:

grep -iE "GoogleAgent-Mariner" /var/log/nginx/access.log \
  | awk '{print $7}' | sort | uniq -c | sort -rn | head -20

Check the requests are genuine

Anyone can send the Project Mariner user-agent, so confirm the source before acting on a match:

GoogleAgent-Mariner: we hold no published IP list, so use reverse DNS where the operator documents a hostname and treat an unverifiable Project Mariner request with caution.

Frequently Asked Questions

What user-agent string does Project Mariner use?

Project Mariner is reported to identify itself with GoogleAgent-Mariner. Evidence that the spelling is in real use comes from our own robots.txt study: 69 of the 5,583 valid robots.txt files in the Tranco top 10,000 name it (fetched October 20, 2026), 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?

Will blocking Project Mariner hurt my SEO?

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.