AI crawlers are automated bots that AI companies use to fetch web content, either to help train their models or to retrieve live information when answering a question. They identify themselves with user-agent names like GPTBot, ClaudeBot, PerplexityBot, and Google-Extended, they obey or ignore your robots.txt depending on the operator, and importantly, many of them fetch raw HTML and do not execute JavaScript.
In short
- AI crawlers fetch web content for model training and for live retrieval when answering questions.
- Major ones include GPTBot, OAI-SearchBot, ClaudeBot, PerplexityBot, and Google-Extended.
- They fall into training crawlers, search and retrieval crawlers, and user-triggered fetchers.
- Many do not execute JavaScript, so client-side rendered content can be invisible to them.
What is an AI crawler?
An AI crawler is a bot operated by an AI company to collect content from the web. Like a traditional search engine crawler, it requests pages over the internet and reads what the server returns, but its purpose is to feed AI systems rather than a conventional search index.
These crawlers identify themselves through a user-agent string, a label sent with each request that names the bot, which is how you can see them in your server logs and how you can set rules for them. Most major AI operators publish the user-agent names and the IP ranges their crawlers use, so you can identify and manage them. Understanding which crawlers visit your site, and what each is for, is the starting point for deciding how to handle them, covered in should you allow or block AI crawlers.
What are the main AI crawlers?
The main AI crawlers come from the large AI and search companies, and each operator typically runs more than one for different purposes. Knowing the common names helps you identify them in logs and set rules deliberately.
The widely seen ones include several families. OpenAI operates GPTBot, generally associated with collecting training data, along with crawlers associated with live browsing and search such as OAI-SearchBot and a user-triggered fetcher for ChatGPT. Anthropic operates ClaudeBot and related agents that fetch content for Claude. Perplexity operates PerplexityBot and a user-triggered fetcher for live answers. Google operates Google-Extended, a control that governs use of your content for its AI products, alongside its general crawlers, and AI Overviews draw on Google's existing index. Other operators, including Microsoft and Meta, run their own crawlers as well. The exact names, behaviors, and controls change over time as operators update them, so it is worth checking current documentation rather than relying on a fixed list.
What types of AI crawlers are there?
AI crawlers fall into three broad types by purpose: training crawlers, search and retrieval crawlers, and user-triggered fetchers. The distinction matters because you may want to treat them differently.
The three types behave differently. Training crawlers collect content to help train or improve models, so the content they gather may influence future model versions rather than today's answers. Search and retrieval crawlers fetch content to answer questions in AI search features, so the content they gather can appear in current answers with citations. User-triggered fetchers retrieve a specific page when a user asks about it or pastes a link, fetching on demand rather than crawling broadly. This split is why some brands choose to allow the search and retrieval crawlers, which feed cited answers and drive visibility, while making a separate decision about training crawlers, a choice covered in should you allow or block AI crawlers.
Do AI crawlers run JavaScript?
Many AI crawlers do not run JavaScript. They fetch the raw HTML your server returns and read that, without executing the scripts that a browser would run to build the rest of the page. This is one of the most important technical facts in LLM optimization.
The consequence is direct and often missed. If your page assembles its content client-side, meaning the initial HTML is mostly empty and JavaScript fills it in once it runs in the browser, then a crawler that does not execute JavaScript sees an empty or near-empty page, even though the page looks complete to a person. Google's own crawler does render JavaScript, and AI Overviews rely on Google's index, so Google-based surfaces are less exposed, but several dedicated AI crawlers are not. The safe approach is to serve your important content in the initial HTML through server-side rendering, static generation, or prerendering, which is covered in detail in how to fix JavaScript rendering issues that block AI crawlers.
How can you see AI crawlers on your site?
You can see AI crawlers on your site by examining your server logs for their user-agent strings, which reveals which bots are visiting, how often, and which pages they fetch. This is the most reliable way to know whether AI systems are actually crawling your content.
A few approaches help. Server-side logs record every request with its user-agent, so filtering for known AI crawler names shows their activity directly. Some analytics and log-analysis tools can surface AI crawler traffic specifically. Watching this over time tells you whether your content is being fetched, whether new crawlers have appeared, and whether a change you made, such as fixing rendering or adjusting robots.txt, affected crawler behavior. Setting up this monitoring is part of measuring AI visibility on the technical side, complementing the answer-side tracking covered in how to measure AI visibility. If you expect AI crawlers but see none in your logs, that is a signal to check whether they are being blocked.