Short answer
robots.txt is a file at a site’s root that tells automated crawlers which paths they may request. It is advisory rather than enforced, applies per user-agent, and is the file that determines whether AI crawlers such as GPTBot, ClaudeBot and PerplexityBot are permitted to read a site at all.
Also called: Robots exclusion protocol
The most common self-inflicted AI-visibility problem lives here: a robots.txt copied from another project, or a blanket disallow added during development, that quietly blocks the crawlers behind the answer engines. A site cannot be cited by a system that was never allowed to read it.
Blocking is a legitimate choice — some publishers deliberately exclude AI training crawlers — but it should be a decision rather than an accident, and it is worth distinguishing the crawlers used for training from those used to fetch pages at answer time.
Related terms
llms.txt
llms.txt is a proposed plain-text file at a site’s root that offers language models a curated map of its most useful pages, in Markdown, without navigation and boilerplate.
Generative Engine Optimization (GEO)
Generative engine optimization is the practice of increasing how often a brand or page is used as a source by generative AI systems.
XML Sitemap
An XML sitemap is a machine-readable list of the URLs a site wants crawled, usually with a last-modified date for each.
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