llms.txt: Definition

llms.txt

Also: llms.txt file, llms.txt standard

llms.txt is a markdown file at a site's root that gives AI systems a curated map of its most important content. As of 2026 it is not a Google Search or AI Overviews ranking signal, but Google's Chrome Lighthouse now audits for it as an agentic-browsing best practice, so it is becoming low-cost infrastructure for helping AI agents navigate your site.

Updated May 31, 2026

There are two layers to llms.txt, and they pull in different directions. For search visibility, Google is clear that llms.txt does nothing: its guidance on AI features says AI Overviews and AI Mode draw from the normal Search index, with no special files required.

For agentic browsing, the picture changed in May 2026, when Google added an llms.txt audit to Chrome Lighthouse under a new agentic-browsing category. Google's framing is that without the file, AI agents may spend more time crawling a site to understand its structure. So it is positioned as a convenience for autonomous agents, not a ranking factor.

The practical takeaway: an llms.txt file is now cheap, sanctioned infrastructure worth adding for agent-friendliness, but it is not a shortcut to AI citations or higher rankings. Prioritize reachability and answer-first structure first, then add llms.txt as housekeeping.