Lighthouse starts checking llms.txt
In Lighthouse 13.3.0 the llms.txt check is on by default - what exactly it looks at, why an empty file passes and what it does not prove
Lighthouse 13.3.0 came out on May 7, 2026. In it the llms.txt check is on by default in the experimental Agentic Browsing category. A week earlier, in version 13.2.0, the check appeared in the code.
Lighthouse is the Chrome team’s tool for checking page speed, accessibility and SEO. Its report now has a line about a file for agents.
What is checked
One fact: whether /llms.txt answers.
| Site response | What the report shows |
|---|---|
| The file is served | the check passes |
Status 404 | “not applicable” |
| Server error | a warning |
Lighthouse does not read the content of the file. An empty file and a thought-out map are equal for the check.
Why it is a notable event
Before May 2026 no mainstream tool for site owners mentioned llms.txt. Now everyone who opens a Lighthouse report learns about the file.
What the check does not mean
- It is not a signal for Google Search. A month later Google wrote in its documentation that Search does not use such files.
- A missing file does not lower the performance, accessibility or SEO scores.
- The category is experimental and has no overall score.
What a site owner should do
Creating an empty file for the sake of a line in a report is not worth it: that is how files without a single link appear. If the site has documentation, a catalog or a knowledge base, make a real file and the check will pass by itself. The detailed breakdown: Lighthouse and llms.txt.