Glossary
llms.txt
llms.txt is a proposed standard: a plain-text file at a site's root that indexes what the site offers to AI systems, with an optional llms-full.txt carrying the content itself. Google's documentation says no such file is needed to appear in Search or its AI features.
The proposal is cheap by construction — one file, plain text, no server work — and tooling has made it cheaper still: Ahrefs shipped a free generator in July 2026, built on its own analysis of llms.txt adoption across 137,000 domains. Low cost is most of the argument for publishing it.
Google has answered its half of the open question on the record. Its "AI features and your website" documentation states that you don't need to create new machine readable files, AI text files, or markup to appear in those features. For Google Search and the AI features inside it, the file does nothing. That is a documented answer, not an inference.
What the record does not contain is the other half. No statement from OpenAI, Anthropic, Perplexity or Microsoft about whether their systems read llms.txt appears on this wire, and no study here ties publishing the file to citations anywhere. The adjacent move is better evidenced: publishers have begun serving agent-readable markdown versions of pages outright, and Time is selling ads inside its own.
The record: llms.txtGoogleAhrefs
See also: AEOAI crawlersAgentic searchSEO