Project
Google's free web tool that uses Lighthouse to analyze a page's performance, accessibility, and SEO, scoring it against Core Web Vitals and other metrics.
Version 2 of the llms.txt proposal landed in August, Lighthouse has audited the file since Chrome 13.3, and three of the four big WordPress SEO suites generate one. Google Search still says nothing fetches it.
Reality
Lighthouse's performance score is a weighted average of five lab metrics whose weights add to 100, and the set leaves out Interaction to Next Paint. The 0 to 100 comes entirely from one simulated load, and field data sits next to it.
Reality
PageSpeed Insights needs the origin HTML before it can measure anything, and a scheduled run that gets a bot challenge instead still produces a number. Cloudflare's own documentation decides which allowlist can fix it.
Reality
Chrome starts shipping Stable every fortnight in September 2026 while CrUX keeps averaging 28 days of sessions, so a field LCP move can be version mix rather than anything your team deployed. Label the browser.
Reality
The experimental category grades semantics, CLS, llms.txt and WebMCP, and it is explicitly not a ranking factor. The scoring rule means most sites can pass it without touching an agent.
Reality