This document discusses Core Web Vitals, which are user-centric web performance metrics defined by Google. It introduces the three Core Web Vitals: Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS). Thresholds for what is considered good, adequate, or needs improvement are provided for each metric. The document also outlines tools that can be used to measure Core Web Vitals and explains how real user monitoring is important for field testing Core Web Vitals performance.