Definition
llms.txt is a proposed Markdown file placed at a website’s root that describes the site and links to its key resources, helping AI agents navigate it. It is an optional bonus — Google says it is not required to appear in generative search.
llms.txt is a proposed standard file (served at /llms.txt) that gives AI agents a concise, Markdown-formatted map of your site: what it is and where the important content lives. Think of it as a curated table of contents written for machines.
Should you add one?
It is cheap to add and some third-party agents may use it, so it does no harm. But Google has stated plainly that you do not need special AI files to appear in generative search. Treat llms.txt as optional polish after the fundamentals.
Related files
It sits alongside robots.txt (which governs crawling and, via Content-Signal, AI usage) and an optional /.well-known/mcp.json manifest for the Model Context Protocol.
Frequently asked questions
Is llms.txt required for AI search?
No. Google has explicitly said you do not need special AI files, markup, or Markdown to appear in generative search. llms.txt is an optional convenience for third-party agents.
What is the difference between llms.txt and robots.txt?
robots.txt governs whether crawlers may access content (and, with Content-Signal, how AI may use it). llms.txt describes and links your content for agents. See llms.txt vs robots.txt.