Claude-Web (Anthropic): User Agent & robots.txt Block Rules

Q: What is the official user-agent string for Claude-Web?

The official user-agent string for Claude-Web is: Claude-Web. This is the exact string you must use in robots.txt, Nginx, Apache, or Cloudflare firewall rules to target this bot. User-agent matching in robots.txt is case-insensitive, but the string must be spelled correctly. You can verify that a request genuinely comes from Claude-Web by performing a reverse-DNS lookup on the source IP - legitimate bots resolve back to their operator's domain.

Q: How do I block Claude-Web in robots.txt?

Add the following lines to your /robots.txt file: User-agent: Claude-Web Disallow: / This instructs Claude-Web not to crawl any path on your site. The Disallow: / directive covers the entire domain including subfolders. To only block specific sections, replace / with the path (e.g., Disallow: /blog/). Note: robots.txt is publicly readable - any bot or human can inspect it at yourdomain.com/robots.txt.

Q: How do I verify if Claude-Web is crawling my site?

Search your web server access logs for the string Claude-Web (case-insensitive grep: grep -i "Claude-Web" /var/log/nginx/access.log). You can also check Google Search Console → Coverage → Crawl Stats for Googlebot variants. For Claude-Web specifically, filter by user-agent in your log analysis tool (GoAccess, AWStats, etc.).

Quick Facts

User-Agent:: Claude-Web
Category:: AI & LLM Bots
Operator:: Anthropic
Safety:: Safe
Blocking Impact:: Low - No SEO ranking impact
SEO Impact Score:: 2/10
Official docs:: support.claude.com

What is Claude-Web?

Claude-Web is used when a Claude AI user asks the model to visit a specific URL to answer a question.

Claude-Web is used when a Claude AI user asks the model to visit a specific URL to answer a question. Claude-Web is an AI data-collection crawler operated by Anthropic. It harvests web content to build or expand training datasets for large language models (LLMs). Unlike search crawlers, Claude-Web does NOT influence your page ranking in any search engine. The user-agent string Claude-Web can be safely blocked via robots.txt, meta tags (noai), or the emerging llms.txt standard without any SEO penalty. Robots.txt is voluntary; for hard enforcement, combine it with server-level IP blocking.

What happens if you block Claude-Web?

✅ **No SEO Impact** - Blocking Claude-Web does not affect your rankings in Google, Bing, or any other search engine. Claude-Web is an AI training crawler, not a search indexer. You can freely block it via User-agent: Claude-Web / Disallow: / without any SEO penalty. This is the recommended approach if you want to opt out of Anthropic's LLM training datasets.

Generally safe to allow; provides legitimate crawling value.

How to block Claude-Web with robots.txt

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

Block completely (robots.txt)

User-agent: Claude-Web
Disallow: /

Allow all (robots.txt)

User-agent: Claude-Web
Allow: /

Block private only (robots.txt)

User-agent: Claude-Web
Disallow: /private/
Disallow: /api/
Disallow: /admin/
Allow: /

Nginx server block

# Nginx: Hard-block Claude-Web
if ($http_user_agent ~* "Claude\-Web") {
    return 403 "Bot blocked";
}

Apache .htaccess

# Apache: Hard-block Claude-Web
SetEnvIfNoCase User-Agent "Claude\-Web" 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 Claude-Web safe to allow?

Yes, Claude-Web is a **safe and legitimate** crawler. It is operated by Anthropic, which publicly documents its crawler at an official URL and follows the Robots Exclusion Protocol (RFC 9309). The user-agent string Claude-Web is verifiable via reverse-DNS lookup on the crawling IP addresses. You can safely allow it unless you have a specific reason to block (e.g., AI training opt-out or SEO tool visibility).

Verify by reverse-DNS lookup: legitimate Claude-Web requests resolve to anthropic's domain.

What does Claude-Web do?

Understanding Claude-Web's purpose helps you decide whether to allow or block it.

Collects web content for AI model training
Gathers data to improve language understanding
Scrapes text, code, and other content for datasets
May be used for chatbot and AI assistant development
Typically does NOT affect search engine rankings

Frequently Asked Questions

What is the official user-agent string for Claude-Web?

The official user-agent string for Claude-Web is: Claude-Web. This is the exact string you must use in robots.txt, Nginx, Apache, or Cloudflare firewall rules to target this bot. User-agent matching in robots.txt is case-insensitive, but the string must be spelled correctly. You can verify that a request genuinely comes from Claude-Web by performing a reverse-DNS lookup on the source IP - legitimate bots resolve back to their operator's domain.

Is Claude-Web safe?

Yes, Claude-Web is a **safe and legitimate** crawler. It is operated by Anthropic, which publicly documents its crawler at an official URL and follows the Robots Exclusion Protocol (RFC 9309). The user-agent string Claude-Web is verifiable via reverse-DNS lookup on the crawling IP addresses. You can safely allow it unless you have a specific reason to block (e.g., AI training opt-out or SEO tool visibility).

Will blocking Claude-Web hurt my SEO?

✅ **No SEO Impact** - Blocking Claude-Web does not affect your rankings in Google, Bing, or any other search engine. Claude-Web is an AI training crawler, not a search indexer. You can freely block it via User-agent: Claude-Web / Disallow: / without any SEO penalty. This is the recommended approach if you want to opt out of Anthropic's LLM training datasets.

How do I block Claude-Web in robots.txt?

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

User-agent: Claude-Web
Disallow: /

This instructs Claude-Web not to crawl any path on your site. The Disallow: / directive covers the entire domain including subfolders. To only block specific sections, replace / with the path (e.g., Disallow: /blog/). Note: robots.txt is publicly readable - any bot or human can inspect it at yourdomain.com/robots.txt.

Does Claude-Web respect robots.txt?

Yes - Claude-Web is a well-behaved bot operated by Anthropic. It fetches and parses /robots.txt before crawling any page, following RFC 9309.

How do I verify if Claude-Web is crawling my site?

Search your web server access logs for the string Claude-Web (case-insensitive grep: grep -i "Claude-Web" /var/log/nginx/access.log). You can also check Google Search Console → Coverage → Crawl Stats for Googlebot variants. For Claude-Web specifically, filter by user-agent in your log analysis tool (GoAccess, AWStats, etc.).

What is the crawl frequency of Claude-Web?

Claude-Web crawls at a moderate rate. If you notice excessive traffic in your logs, you can add a Crawl-delay directive:

User-agent: Claude-Web
Crawl-delay: 10

(10 second delay between requests).

Can I block Claude-Web from specific pages only?

Yes. Instead of a global Disallow: / you can restrict Claude-Web to specific paths:

User-agent: Claude-Web
Disallow: /private/
Disallow: /staging/
Allow: /

This allows Claude-Web everywhere except the listed paths. Path matching in robots.txt uses prefix matching - Disallow: /private/ blocks /private/page.html but NOT /public/private/.

Does blocking Claude-Web prevent AI training on my content?

Blocking Claude-Web via robots.txt signals to Anthropic that your content should not be used for AI training. However, robots.txt is a **voluntary** protocol - there is no technical enforcement. For stronger protection: 1. Add <meta name="Claude-Web" content="noai, noimageai, noindex"> to your pages. 2. Add a llms.txt file at your domain root (emerging standard). 3. Use Cloudflare WAF or Nginx to return 403 for this user-agent. 4. Consider IP blocklists for Anthropic's known crawler IP ranges.

Is there an alternative to robots.txt to opt out of Claude-Web?

Yes. Several additional opt-out mechanisms exist for AI crawlers: • **Meta tag**: <meta name="Claude-Web" content="noindex"> • **X-Robots-Tag HTTP header**: X-Robots-Tag: noai, noimageai • **llms.txt**: Add a /llms.txt file (similar to robots.txt but for LLMs) • **Server block**: Return 403 or 429 for this user-agent via WAF or Nginx Using multiple layers provides the strongest protection.