Understanding AI Crawlers: Who's Reading Your Website?

If you've checked your server logs lately, you've probably noticed some unfamiliar names: GPTBot, ClaudeBot, PerplexityBot. These aren't your parents' search engine crawlers.

We see questions about these bots constantly, so let's break down who they are, what they want, and whether you should let them in.

Three categories

Not all AI bots are the same. There are three categories:

1. Training bots — collecting content to train AI models (GPTBot, ClaudeBot)
2. Search bots — crawling to power AI search features (OAI-SearchBot, PerplexityBot)
3. User-triggered fetchers — grabbing a page because someone asked the AI to look at it (ChatGPT-User, Claude-User)

The distinction matters. Blocking training bots doesn't necessarily make you invisible to AI. Search bots and user fetchers can still find you.

Want the full optimization playbook? See: How to Improve Your AI-Readiness Score.

The bots you'll see in your logs

OpenAI's fleet

OpenAI actually runs three different bots, which is smart: it lets you make granular decisions about what you allow.

• GPTBot — the training crawler. This is what collects content to improve their models.
• OAI-SearchBot — powers ChatGPT's search feature. If you want to show up in ChatGPT search results, this is the one that matters.
• ChatGPT-User — fires when a user explicitly asks ChatGPT to "look at this page." It's basically acting on behalf of a human.

Anthropic's bots (Claude)

Anthropic follows a similar pattern—separate tokens for separate purposes:

• ClaudeBot — training data collection
• Claude-User — when a Claude user asks it to fetch a specific URL
• Claude-SearchBot — crawls for Claude's search capabilities

PerplexityBot

Perplexity is interesting because it's search-first—their whole product is about finding and citing sources.

• PerplexityBot — their main search crawler
• Perplexity-User — user-triggered fetches

Heads up: Perplexity's docs say their user-triggered fetcher generally ignores robots.txt. The logic is that if a human asked the AI to look at a page, blocking it would be like blocking a human with a browser. Controversial, but that's their stance.

Google-Extended

This one confuses people. Google-Extended is not Googlebot. It's a separate token specifically for Gemini (Google's AI) training and grounding.

Blocking Google-Extended does not affect your Google Search rankings. Google has been explicit about this. It only controls whether your content gets used in Gemini's training data.

How these differ from Googlebot

Technically, they're pretty similar. They make HTTP requests, parse HTML, follow links. The difference is what happens after they crawl:

• Search bots (Googlebot) → index your page → show it in search results
• AI training bots (GPTBot, ClaudeBot) → feed content into model training
• AI search bots (OAI-SearchBot, PerplexityBot) → use content to generate answers with citations

One thing we've noticed: AI crawlers are less predictable than Googlebot. They don't follow a neat schedule. Some sites see them daily, others weekly, others rarely.

What makes your site attractive to AI crawlers

We don't have insider knowledge of their ranking algorithms (nobody outside these companies does), but based on what we've observed and what these companies have said publicly:

Content that works:

• Clear, informative writing (not marketing fluff)
• Obvious structure—headings that actually describe what follows
• Facts and specifics, not vague claims
• Answers to questions people actually ask

Technical stuff that helps:

• Fast pages (bots have timeouts too)
• Clean HTML—less cruft means easier parsing
• Structured data (Schema.org)—we wrote a whole guide on this: Structured Data for AI

Trust signals:

• Who wrote this? When?
• Are there sources for non-obvious claims?
• Is this a real organization with a real About page?

How to configure access

If you want AI Visibility (most sites)

This is what we recommend for most public sites. Allow everything:

User-agent: GPTBot
Allow: /

User-agent: OAI-SearchBot
Allow: /

User-agent: PerplexityBot
Allow: /

User-agent: ClaudeBot
Allow: /

User-agent: Claude-SearchBot
Allow: /

User-agent: Google-Extended
Allow: /

You can also take a middle-ground approach: allow search bots but block training bots. That way you can appear in AI search results without your content being used to train models.

If you want to opt out completely

Your call. Here's how:

User-agent: GPTBot
Disallow: /

User-agent: ClaudeBot
Disallow: /

User-agent: Google-Extended
Disallow: /

If you want granular control

Most sites have some pages that should be public and others that shouldn't. Here's an example:

User-agent: GPTBot
Allow: /blog/
Allow: /products/
Disallow: /admin/
Disallow: /private/

Important: robots.txt controls crawling, not indexing. If a URL is linked from somewhere else, search engines might still index it even if you've blocked crawling. For truly private content, use authentication or noindex tags.

Why this matters for your business

We'll be direct: if AI can't read your site, it can't cite you.

When someone asks ChatGPT or Perplexity about your industry, do you show up? If you've blocked their crawlers, probably not. Your competitors who are accessible will get mentioned instead.

That said, there are legitimate reasons to block training crawlers—copyright concerns, licensing issues, competitive intelligence. Just know the tradeoff.

What we recommend

Check your logs. Do you even know which bots are visiting? We've talked to site owners who had no idea GPTBot was hitting them daily.

Keep content fresh. We've noticed AI systems tend to prefer recent content. An article from 2019 is less likely to be cited than one from 2024.

Use structured data. It's not required, but it helps. See our guide: Structured Data for AI.

Test your AI Visibility. We built friendly4AI specifically for this—scan your site and see what AI crawlers see. To understand how LLMs decide which sites to mention, read What Is AI Visibility? and How LLMs Choose Which Websites to Recommend.

Keep reading

• How LLMs Choose Which Websites to Recommend — training data vs. retrieval, per-platform differences
• What is AI-readiness? — the bigger picture
• Structured Data for AI — help machines understand your content
• How to Improve Your AI-Readiness Score — the full checklist
• What Is AI Visibility? — why LLMs recommend some sites but not others

FAQ

How do I find AI crawlers in my logs?

Grep for these User-Agent strings: GPTBot, OAI-SearchBot, ChatGPT-User, ClaudeBot, Claude-SearchBot, Claude-User, PerplexityBot, Perplexity-User, Google-Extended.

If you're using a CDN or analytics platform, many now have built-in bot detection that separates AI crawlers from regular traffic.

Will blocking training bots make me invisible to AI?

Not entirely. You can block training bots (GPTBot, ClaudeBot) while allowing search bots (OAI-SearchBot, PerplexityBot). The search bots can still find and cite you—your content just won't be used to train models.

Official documentation

We've linked to the official sources here so you can verify everything yourself:

• OpenAI: https://platform.openai.com/docs/gptbot (includes JSON feeds for IP ranges)
• Anthropic: https://support.claude.com/en/articles/8896518-does-anthropic-crawl-data-from-the-web-and-how-can-site-owners-block-the-crawler
• Google-Extended: https://developers.google.com/crawling/docs/crawlers-fetchers/google-common-crawlers
• Perplexity: https://docs.perplexity.ai/guides/bots

This space is evolving fast. New bots appear, policies change, tokens get added. We try to keep this page updated, but always check the official docs for the latest.