If you've opened Chrome DevTools lately and run Lighthouse, you may have noticed a new category sitting under Performance, Accessibility, SEO and the rest: Agentic Browsing.
It shipped in Lighthouse 13.3 (May 2026). It's still marked experimental, so it doesn't give you a 0–100 score — just a pass/fail per check. But "experimental" in Lighthouse has a way of becoming "default, and now your client is asking why it's red." So it's worth understanding now, while it's cheap.
The category answers one question: can an AI agent actually understand and operate this page? It does that with four checks. Here's what each one tests and exactly how to make it pass.
1. llms.txt
What it checks: whether your domain root serves an /llms.txt, and — this is the part people miss — whether that file is actually useful: it flags the file if it's missing an H1, is too short, or contains no links.
