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An AI crawler is an automated web client used by an AI-related service to fetch pages or other online resources. The term covers different activities: a crawler may collect content for possible model training, help an AI search service discover websites, or fetch a page after a user asks an assistant to inspect it. A request from an AI-associated bot does not, by itself, mean the page is being used to train a model.
What does an AI crawler do?
A crawler sends requests to websites to retrieve pages or other resources. The service operating it determines what happens next. For example, OpenAI distinguishes between GPTBot, which it says crawls content that may be used to train its generative AI foundation models, and OAI-SearchBot, which it uses to surface websites in ChatGPT search. A user-triggered fetch is different again.
That distinction matters when deciding whether to allow a bot. Blocking a crawler associated with one purpose may have a different effect from blocking another, even if both relate to AI products.
How do GPTBot, ClaudeBot and other named crawlers differ?
The names below describe documented or directory-listed bots, not a complete or permanent catalog. Vendors can change their products, crawler names, and policies. For details about how a particular bot uses content, rely on that vendor’s current documentation where available.
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| Name | Documented or listed role | What to keep in mind |
|---|---|---|
| GPTBot | OpenAI says it crawls content that may be used to train its generative AI foundation models. OpenAI’s bot documentation | OpenAI describes blocking GPTBot as indicating that content should not be used for that training purpose. It is separate from the control for ChatGPT search. |
| OAI-SearchBot | OpenAI says it helps surface websites in ChatGPT search features. OpenAI’s bot documentation | Opting out can prevent a site from appearing in ChatGPT search answers, although navigational links may still appear. |
| ChatGPT-User | OpenAI says it is used for certain visits initiated by a user in ChatGPT or a custom GPT. OpenAI’s bot documentation | It is not the automatic crawler used for search inclusion. OpenAI notes that robots.txt may not apply to these user-initiated actions. |
| Google-Extended | A robots.txt product token for controlling certain uses of crawled content in future Gemini training and grounding. Google’s crawler documentation | It is not a separate HTTP user-agent string. Google says it does not affect inclusion in Google Search or act as a Search ranking signal. |
| ClaudeBot | Listed as an Anthropic crawler in Cloudflare’s AI crawler reference. Cloudflare’s verified-bot reference | Check Anthropic’s current first-party documentation before relying on a detailed claim about its use or policy behavior. |
| PerplexityBot | Listed as a Perplexity AI search crawler in Cloudflare’s reference. Cloudflare’s verified-bot reference | Check current first-party documentation for the exact scope and effect of blocking it. |
| Bytespider | Listed with ByteDance in Cloudflare’s reference. Cloudflare’s verified-bot reference | A user-agent string can be copied or spoofed, so the name in a request alone does not prove its source. |
| Meta-ExternalAgent | Listed with Meta in Cloudflare’s reference. Cloudflare’s verified-bot reference | Treat it as a directory entry, not a complete history of Meta’s crawler names. |
Does robots.txt stop AI crawlers from using your content?
robots.txt lets a site owner publish crawler access rules, but it is not a security barrier. The Internet Engineering Task Force’s RFC 9309 states: “These rules are not a form of access authorization.” A crawler that chooses not to honor the rules—or a client that does not identify itself honestly—can still request a resource that is publicly accessible.
Use authentication, permissions, or another server-side access control for private or sensitive material. Do not rely on a robots.txt rule to keep it secret.
When a crawler honors robots.txt, the file can communicate that it should not fetch specified paths. The effect depends on the crawler and vendor. For example, OpenAI documents separate controls for GPTBot and OAI-SearchBot, while Google documents Google-Extended as a product token used with existing Google crawler requests.
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Google-Extended is a standalone robots.txt token, not a distinct request user-agent. Google says it can control certain uses of crawled content for future Gemini training and grounding. It does not change whether a site is included in Google Search and is not a Search ranking signal.
Keep this separate from Google Search presentation controls. Google’s robots meta tag and X-Robots-Tag guidance governs how Google presents accessible content in Search. Googlebot must be able to fetch a page to read a page-level meta directive on it; if crawling is blocked, that directive cannot be read from the page. See Google’s robots meta tag and X-Robots-Tag documentation.
How can you decide whether to allow or block an AI crawler?
Start with the outcome you want to control, then apply the specific vendor control that addresses it. There is no universal allow-all or block-all rule that preserves every benefit while preventing every unwanted use.
- Define the goal. Decide whether you are concerned about possible training use, visibility in an AI search product, request volume, or keeping material private. Those are different problems and may require different controls.
- Identify the exact bot or token. Use the vendor’s documented product token rather than assuming every AI-related crawler has the same function. OpenAI lists separate robots.txt controls for GPTBot and OAI-SearchBot; Google documents Google-Extended as a token used with existing Google user-agent requests.
- Check the consequence before blocking. Consider whether the rule could reduce visibility in a search or answer product. OpenAI says opting out of OAI-SearchBot can prevent display in ChatGPT search answers, while navigational links may still appear.
- Choose the right enforcement layer. Use robots.txt for crawler access requests, indexing directives for Search presentation, and authentication or server-side permissions for content that must remain private. A CDN or web application firewall can also be part of bot-traffic management.
- Verify the requester and review traffic. User-agent strings can be spoofed. Check server or CDN logs and vendor identity-verification guidance rather than treating a claimed name as proof of identity. Google specifically cautions site owners to verify crawler identity.
- Allow for changes to take effect. OpenAI says a robots.txt update may take approximately 24 hours to affect its search systems. That is vendor-specific guidance, not a general propagation guarantee for all crawlers.
What an AI crawler list can—and cannot—tell you
A crawler directory is a useful starting point for recognizing names in traffic logs, but it is not a permanent or exhaustive roster. Cloudflare’s reference lists several AI-related crawlers, including ClaudeBot, PerplexityBot, Bytespider, and Meta-ExternalAgent. For a specific vendor’s purpose, identity checks, and response to robots.txt, consult that vendor’s current documentation where available.
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Google describes robots.txt as a way for site owners to declare how crawlers should interact with pages, and the protocol is an instruction mechanism rather than access authorization. The practical question is therefore not just “Is this an AI bot?” but “Which bot is requesting what, for what stated purpose, and which control affects the outcome I care about?”
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