How is website performance measured using Core Web Vitals and KPIs?

Website performance is measured using two categories of data: lab data (controlled measurements from tools like Lighthouse run in a consistent environment) and field data (real-world measurements from actual users, collected through the Chrome User Experience Report and surfaced in Google Search Console’s Core Web Vitals report and PageSpeed Insights).

Core Web Vitals targets are: LCP under 2.5 seconds (measures loading performance), CLS below 0.1 (measures visual stability), and INP under 200 milliseconds (measures responsiveness to user input). Supplementary KPIs include Time to First Byte (TTFB, under 800ms), Total Blocking Time (TBT, under 200ms in Lighthouse lab tests), and page weight (total transfer size, ideally under 1MB for a marketing page). Performance should be monitored continuously using a tool like Datadog, SpeedCurve, or Calibre to detect regressions introduced by content updates, plugin additions, or third-party script changes.