Indexly
AI & LLMsUpdated April 27, 2026

AI bots

Definition

AI bots are the automated crawlers operated by AI companies to fetch web content for training and retrieval. The major AI bots in 2026 are GPTBot and ChatGPT-User (OpenAI), ClaudeBot and anthropic-ai (Anthropic), PerplexityBot, Google-Extended (Gemini), and Bytespider (ByteDance). Whether your robots.txt allows them determines whether your content can be cited inside AI assistants.

How AI bots work

Each AI provider runs its own crawler, declared via a distinct user-agent string in HTTP requests:

  • GPTBot (OpenAI): training crawler. Respects robots.txt.

  • ChatGPT-User (OpenAI): on-demand fetch when a ChatGPT user explicitly clicks a link or asks for a page summary.

  • ClaudeBot and anthropic-ai (Anthropic): training and retrieval crawlers respectively.

  • PerplexityBot: powers Perplexity's retrieval-grounded answers.

  • Google-Extended: Google's separate user agent for Gemini and AI Overviews. Allowing Googlebot does not automatically allow Google-Extended.

  • Bytespider (ByteDance): broad-purpose AI training crawler. Often blocked by publishers due to aggressive crawl behavior.

Bots fetch HTML, follow links, parse structured data (Article, FAQPage, BreadcrumbList JSON-LD), and feed content into either training pipelines or live retrieval indices.

AI bots vs traditional search bots

Googlebot fetches pages to populate the SERP. AI bots fetch pages to populate the AI answer.

The two stacks share the basics — robots.txt compliance, sitemaps, structured data — but diverge in three important ways:

  1. Different user agents. Allowing Googlebot does not automatically allow GPTBot or ClaudeBot. Each AI bot is a separate user-agent string.

  2. Different rendering tolerance. Most AI bots execute less JavaScript than Googlebot. Server-side rendering or pre-rendering is typically required.

  3. Different signal weights. Schema, atomic definitions, and dateModified carry more weight in AI bot indexing than in traditional Google indexing.

6+

Major AI bots a publisher should configure in robots.txt

Indexly

0

AI citations earned by pages blocked from AI bots

Indexly framework

Days

Typical lag between AI bot fetch start and first AI citation for a new page

Indexly observation

Why it matters

AI bot access is the gating prerequisite for every downstream AI visibility metric. Pages blocked from AI bots cannot be cited, mentioned, or surfaced in ChatGPT, Claude, Perplexity, or AI Overviews — regardless of authority, freshness, or schema.

AI bot fetches are also a leading indicator. Pages that GPTBot or PerplexityBot starts fetching today tend to start earning citations within days. Server log analysis of AI bot traffic surfaces upcoming AI visibility shifts before citation tracking does.

How to configure AI bots in robots.txt

Five practices for AI bot configuration:

  1. Default to allow. Unless you have a clear reason to block, allow all major AI bots. Blocking forfeits AI visibility entirely.

  2. Allow each bot explicitly. Avoid relying on User-agent: * defaults. Spell out GPTBot, ChatGPT-User, ClaudeBot, anthropic-ai, PerplexityBot, and Google-Extended.

  3. Block aggressive crawlers selectively. Bytespider is the most common opt-out due to crawl rate. Block specific paths if needed (e.g. /admin).

  4. Verify with server logs. robots.txt is advisory. Track actual AI bot fetches in your logs to confirm intended bots are crawling and unwanted ones aren't.

  5. Publish an llms.txt. A complement to robots.txt that surfaces your most authoritative pages. Adoption is growing — cost is near zero.

Frequently asked questions

Should I allow AI bots in robots.txt?

For most publishers, yes. Blocking AI bots forfeits AI search visibility entirely — no citations, no mentions, no AI-referred traffic. Block deliberately if you have a reason (legal, contractual, paywalled); otherwise the default should be allow.

What's the difference between GPTBot and ChatGPT-User?

GPTBot is OpenAI's training crawler — it visits pages proactively for index building. ChatGPT-User is the on-demand fetcher that runs when a ChatGPT user explicitly clicks a link or asks for a page summary. Both should be allowed for full AI visibility.

Does allowing Googlebot cover Google-Extended?

No. Google-Extended is a separate user agent for Gemini and AI Overviews training and retrieval. Allowing Googlebot covers traditional search; you need to explicitly allow Google-Extended for AI Mode and AI Overviews to use your content.

How can I tell which AI bots are crawling my site?

Check server logs for AI user-agent strings. Most AI bots identify themselves clearly (GPTBot, ClaudeBot, PerplexityBot). Indexly aggregates this automatically into agent-analytics dashboards showing fetch frequency per bot per page.

Are AI bots safe to allow at scale?

Generally, yes — major AI bots respect robots.txt and crawl at reasonable rates. Bytespider is the most common bot to block due to aggressive crawl behavior. If a bot exceeds reasonable rate, block it specifically rather than blanket-blocking all AI bots.

Related terms

AI indexing

AI indexing is the process by which AI assistants — ChatGPT, Claude, Gemini, Perplexity, Grok, and Google AI Overviews — crawl, parse, embed, and store web content so it can be retrieved and cited at inference time. It is the AI-search counterpart to Google's traditional index, and the gateway any page must pass through to be eligible for citation.

AI grounding

AI grounding is the practice of anchoring an LLM's response in retrieved, citable sources at inference time — instead of letting the model rely solely on its training memory. Grounding is what separates a hallucination-prone chatbot from a search-grade AI assistant like Perplexity, Google AI Overviews, Bing Chat, or retrieval-augmented ChatGPT.

llms.txt

llms.txt is a proposed web standard — a markdown-formatted file placed at the root of a website — that gives LLMs and AI tools a curated index of a site's most important content. Modeled on robots.txt and sitemap.xml but designed for LLM comprehension rather than search crawlers, llms.txt is in the early adoption phase as of 2026, with no major AI platform officially committed to consuming it.

Generative engine optimization (GEO)

Generative engine optimization (GEO) is the practice of structuring content and brand presence so that AI systems like ChatGPT, Claude, Perplexity, and Google AI Overviews cite, quote, or recommend it when generating answers. Unlike traditional SEO, which competes for ranked positions in a list of links, GEO competes for inclusion inside the answer itself.

AI training data

AI training data is the corpus of text, code, images, and other content used to train large language models. Frontier models like GPT-4o, Claude 4 Sonnet, Gemini 2.5, and Llama 4 are trained on trillions of tokens drawn from web crawls, books, code repositories, and licensed datasets — the composition of which shapes what the model knows, who it cites, and how it represents brands.

AI search visibility

AI search visibility is the umbrella metric capturing how often, how prominently, and how favorably your brand appears across AI assistants — ChatGPT, Claude, Perplexity, Gemini, Grok, and Google AI Overviews. It bundles mentions, citations, ranking position, sentiment, and AI-referred traffic into the executive-level read of a brand's standing in AI search.