llms.txt
llms.txt is a plain-text file at the root of a site that lists the pages worth quoting and says what each one answers, acting as a curated map for language models rather than a complete index.
It is not a sitemap. A sitemap lists everything a crawler should know exists; llms.txt lists the handful of pages that are worth an answer engine's attention, with a line describing what each one covers. That description is the part a model cannot work out on its own from a URL.
Support is a convention rather than a standard, and no engine has committed to reading it. It costs almost nothing to publish, it is trivially verifiable, and it makes a site's own view of its best content explicit.
Related
Answer engine optimisation (AEO)
Answer engine optimisation is the practice of structuring a site so that AI assistants such as ChatGPT, Claude, Perplexity and Google's AI Overviews name and cite it when answering a question, rather than optimising for a position in a list of links.
robots.txt
robots.txt is a file at the root of a site that tells automated crawlers which paths they may request, using per-agent rules.
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