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Lighthouse and llms.txt

What the llms.txt audit in Lighthouse and PageSpeed Insights means, when it appeared, what exactly it checks, what it does not prove, and whether to create the file for the sake of the report

experimental category Chrome documentation

How the audit arrived

Section titled “How the audit arrived”

  1. version

    Lighthouse 13.2.0

    The llms.txt audit lands in the code.

  2. version

    Lighthouse 13.3.0

    The audit is on by default in the Agentic Browsing category.

    Release 13.3.0

  3. news

    The agent-ready toolkit

    Chrome describes how to prepare a site for agents.

    Chrome blog

  4. version

    Lighthouse 13.4.1

    The audit becomes available through the PageSpeed Insights API.

  5. version

    Lighthouse 13.5.0

    Agent discovery audits are gathered into one group.

How it unfolded: the check turned on by default, discovery checks grouped.

What exactly is checked

Section titled “What exactly is checked”
The site’s answer at /llms.txt What Lighthouse reports
The file is served the audit passes
404 “not applicable”: a missing file is not an error
A server error a warning

Three things worth knowing:

  • Content is not judged. An empty file and a careful map are equal to the audit.
  • The category has no overall score. There is no familiar 0 to 100 number for Agentic Browsing.
  • The category is experimental and needs a recent Chrome. Its set of audits changes between releases.

Hence a trap: when a site answers any unknown address with a 200 page, the audit may pass without a file. How to make sure the file is real: Validating files and markup.

Chrome and Search talk about different things

Section titled “Chrome and Search talk about different things”
Two Google products

Chrome, Lighthouse

preparing a site for agents

  • Checks that llms.txt exists
  • Speaks about agents working in a browser
  • Does not claim that Google products read the file

Google Search

index and ranking

  • Does not use llms.txt
  • The file neither helps nor harms rankings
  • Ordinary SEO applies to AI features of Search

There is no contradiction

Lighthouse checks how convenient a site is for agents. The Search documentation describes how results are built. These are different tasks.

Should you create the file for the report

Section titled “Should you create the file for the report”

What is known and what is not

Confirmed

  • Lighthouse checks whether /llms.txt answers.
  • A missing file does not lower the familiar performance, accessibility and SEO scores.
  • The audit is described in the Chrome documentation.

Not proven

  • That passing the audit affects rankings or appearance in AI answers.
  • That the category will stay as it is: it is experimental.

What it does not mean

  • It is not a confirmation that the file is well made.
  • It is not a signal for Google Search.

The Lighthouse audit shows that Chrome is aware of the format. It is not a reason to create the file.

Create the file when the site has material an agent benefits from finding fast: documentation, a catalog, a knowledge base. The Lighthouse audit will then pass as a side effect.

Creating an empty file to clear a line from the report is pointless: that is how files without a single link appear.

Section titled “What to read next”