Lighthouse adds an llms.txt check to its agentic browsing audits
Google’s Lighthouse tool now checks llms.txt in an experimental “agentic browsing” category. It looks for an H1, a link and some content, nothing more.
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What happened?
Lighthouse 13.2.0, released on 1 May 2026, added an “agentic browsing” category with an llms.txt check (its release notes: “config: implement llms.txt check for AI agents”). Lighthouse 13.3.0, on 7 May, made the category part of the default run. Chrome’s documentation calls it “experimental and based on proposed standards”, and testing it needs Chrome 150 or later.
What does the audit check?
The audit is titled “llms.txt follows recommendations”. From its source code:
| Result | When |
|---|---|
| Fails | The request errors, or the server answers with a 5xx or 429 |
| Not applicable | Any other 4xx, such as a 404 for a site without a file |
| Fails: “File is missing a required H1 header” | No # Title line |
| Fails: “File does not appear to contain any links.” | No Markdown link |
| Fails: “File is suspiciously short.” | Fewer than 50 characters |
A Chrome blog post in June described the category as “informational and unbenchmarked”. Lighthouse 13.5.0, in September, grouped the llms.txt check with other agent discovery audits.
What does it mean for your site?
This is a quality check in a developer tool, not a sign that Google Search uses the file. Google’s Search guidance still says Search ignores llms.txt.
Not having a file costs you nothing here: a 404 is “not applicable”. If you do publish one, it should pass, and a broken file that returns a server error fails. The validator checks the same basics plus links, descriptions and how the file is served.