Google says you don't need llms.txt. Google is also checking for it.

Google says you don't need llms.txt. Google is also checking for it.

Google says you do not need llms.txt. Google also just added an llms.txt check to Lighthouse. Both statements are true. They are not contradictory. They are describing two different audiences.

Google Search's AI optimization guide, published earlier this month, placed llms.txt in the mythbusting section. You do not need it for AI Overviews or AI Mode. That guidance is accurate for the Google Search use case. AI Overviews and AI Mode pull from Google's existing search index. If your pages are crawlable, indexable, and well-structured, you are in the pool. The file adds nothing to that process.

Lighthouse 13.3 shipped a new Agentic Browsing category that checks for llms.txt alongside WebMCP support, layout stability, and accessibility structure. This audit does not measure search visibility. It measures whether your site is ready for software agents operating through Chrome agents that need to understand your site's structure, purpose, and primary content without crawling every page to figure it out. Google's own documentation explains the purpose: without llms.txt, agents may spend more time crawling the site to understand its high-level structure.

Two products. Two audiences. Two different readiness requirements.

This is the same distinction that runs through every agentic commerce infrastructure conversation. Google Search AI features query the index. Browser-based agents interact with the site directly. An agent completing a task on a consumer's behalf through Chrome needs to navigate, understand, and execute, not just retrieve a cited paragraph. The llms.txt file is the site's way of telling that agent where to start.

The practical implication: if your team is using "Google said we don't need it" to close the llms.txt conversation, show them the Lighthouse audit. The question is not whether you need it for Search. The question is whether browser agents can navigate your site efficiently when they arrive.

Those are not the same question. Google is now measuring both.