Safe Official docs AI & LLM Bots

Diffbot Fetcher

Operated by Diffbot

Quick Facts

User-Agent:
Diffbot-User
Category:
AI & LLM Bots
Operator:
Diffbot
Safety:
Safe
Blocking Impact:
Low - No SEO ranking impact
SEO Impact Score:
2/10
Official docs:
docs.diffbot.com

Confirmed by the operator

Diffbot names Diffbot-User on its own documentation page, linked above. The token, purpose and robots.txt behaviour on this profile come from that page, re-checked on September 22, 2026.

What is Diffbot Fetcher?

Diffbot Fetcher is an on-demand AI fetcher operated by Diffbot. 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 Diffbot's assistant.

Diffbot Fetcher is an on-demand AI fetcher operated by Diffbot. 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 Diffbot's assistant.
Diffbot Fetcher uses the user-agent token Diffbot-User. 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 Diffbot Fetcher?

✅ No SEO Impact - Blocking Diffbot Fetcher does not affect your rankings in Google, Bing, or any other search engine. Diffbot Fetcher 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 Diffbot Fetcher actually visits you? Read how do I monitor AI bot traffic to my website?

How to block Diffbot Fetcher with robots.txt

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

Block completely (robots.txt)
User-agent: Diffbot-User Disallow: /
Allow all (robots.txt)
User-agent: Diffbot-User Allow: /
Block private only (robots.txt)
User-agent: Diffbot-User Disallow: /private/ Disallow: /api/ Disallow: /admin/ Allow: /
Nginx server block
# Nginx: Hard-block Diffbot Fetcher if ($http_user_agent ~* "Diffbot-User") { return 403 "Bot blocked"; }
Apache .htaccess
# Apache: Hard-block Diffbot Fetcher SetEnvIfNoCase User-Agent "Diffbot-User" bad_bot Order Allow,Deny Allow from all Deny from env=bad_bot
Meta robots tag
<meta name="robots" content="noindex, nofollow">
X-Robots-Tag header
X-Robots-Tag: noindex, nofollow

Is Diffbot Fetcher safe to allow?

Yes, Diffbot Fetcher is a safe and legitimate crawler operated by Diffbot. It follows the Robots Exclusion Protocol (RFC 9309) and can be controlled with standard robots.txt rules.
Verify by reverse-DNS lookup: legitimate Diffbot Fetcher requests resolve to Diffbot's domain.

What does Diffbot Fetcher do?

Understanding Diffbot Fetcher'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 is the official user-agent string for Diffbot Fetcher?
The official user-agent string for Diffbot Fetcher is: Diffbot-User. Use this exact string in robots.txt, Nginx, Apache, or Cloudflare firewall rules to target this bot. Matching in robots.txt is case-insensitive. Verify a request genuinely comes from Diffbot Fetcher by performing a reverse-DNS lookup on the source IP.
Is Diffbot Fetcher safe?
Yes, Diffbot Fetcher is a safe and legitimate crawler operated by Diffbot. It follows the Robots Exclusion Protocol (RFC 9309) and can be controlled with standard robots.txt rules.
Will blocking Diffbot Fetcher hurt my SEO?
✅ No SEO Impact - Blocking Diffbot Fetcher does not affect your rankings in Google, Bing, or any other search engine. Diffbot Fetcher 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 Diffbot Fetcher in robots.txt?
Add the following lines to your /robots.txt file:
User-agent: Diffbot-User
Disallow: /

This instructs Diffbot Fetcher not to crawl any path on your site. To block only specific sections, replace / with the path (e.g., Disallow: /blog/).
Does Diffbot Fetcher respect robots.txt?
Diffbot Fetcher is operated by Diffbot and is expected to fetch and parse /robots.txt before crawling, following RFC 9309. For hard enforcement, combine robots.txt with server-level IP or user-agent blocking.
How do I verify if Diffbot Fetcher is crawling my site?
Search your web server access logs for the string Diffbot-User (case-insensitive: grep -i "Diffbot-User" /var/log/nginx/access.log). Filter by user-agent in your log analytics tool (GoAccess, AWStats, etc.).

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