Search Engine Bots vs. LLM Crawlers: Technical Differences
When you look at your server logs, you no longer see only the familiar search engine bots. Crawlers that belong to AI systems also send requests to your site. Both read your pages, but their purposes and behavior are not the same. In this article we cover the technical differences between search engine bots and LLM crawlers.
What Do Search Engine Bots Do?
Classic search engine bots crawl pages, add them to an index and use them to rank results when a query comes in. Their purpose is to place the page correctly in a list. These bots have come with well-known user agent names for years, and their behavior is well documented for site owners.
What Do LLM Crawlers Do?
The crawlers of AI systems can work for different purposes. Some collect content to be used in training a model, while others fetch a page at that moment to produce an answer when a user asks a question. These two uses are not the same thing, and each provider manages them differently. That is why "AI bot" does not describe a single behavior.
How They Process the Page
Some classic search bots can run the JavaScript on a page and see the content. It would be wrong to assume the same for every AI crawler. Having the main content in the first HTML response is the safest way to make sure the text is read, whichever bot arrives. Exact behavior is explained in each provider's own documentation and may change over time.
robots.txt and Identification
Some crawlers of AI systems use their own user agent names such as GPTBot, ClaudeBot and PerplexityBot, and state that they follow robots.txt rules. Google also has a separate robots.txt token for its AI products. The current form of these names and rules should be checked in the providers' documentation. Because a user agent name can easily be faked in a request, you should look at the verification methods a provider publishes when making a decision about a specific bot.
Telling Them Apart in Logs
The user agent field in server logs is the first way to see which crawler came. Looking at which pages they visit and how often shows which part of your site the bots are interested in. A bot that sends requests too often can strain the server, in which case a rate limit or a crawl delay in robots.txt comes into question.
Consequences of Blocking Access
Closing a bot off with robots.txt may limit that system's use of your content. That can be an unwanted result if your goal is to be visible in AI answers. If your goal is to limit the use of your content in model training, a separate decision is needed. Whether you can manage training bots and live answer bots separately varies by provider.
Conclusion
Telling search engine bots and LLM crawlers apart is the first step toward understanding who comes to your site and why. In our GEO optimization service we build a site structure that is open to bots and read correctly. Get in touch if you'd like to review your site's bot access together.
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Frequently Asked Questions
Do search engine bots and LLM crawlers follow the same rules?
Both can follow robots.txt rules, but their user agent names, purposes and behavior differ. You need to check each provider's documentation.
Do AI bots run JavaScript?
This varies from provider to provider. The safe way is to serve the main content in the first HTML response.
If I block one bot, will I lose out in classic search too?
Classic search bots come with separate user agent names. If you write the rule only for the relevant bot, the others are not affected.
How do I see which bots are visiting?
By looking at the user agent field in your server access logs.