PageSpeed Insights (PSI) is a free Google tool that reports both lab performance data (powered by Lighthouse) and real-world field data from the Chrome User Experience Report (CrUX) for a given URL. The field data reflects actual user experiences on that specific page, making it the most direct indicator of how Google perceives the page's performance for ranking purposes. PSI scores pages 0–100 and flags [Core Web Vitals](/glossary/core-web-vitals) as Pass or Fail based on the 75th percentile of real-user measurements over the preceding 28 days.