Core Web Vitals are three real-world performance metrics that Google uses to measure the user experience of a web page. They became a ranking signal in Google's Page Experience update and directly affect how high your pages appear in search results.
The three metrics are Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift. Each one measures a different aspect of how the page feels to a real person. Not a lab test. Not a synthetic benchmark. Observed experience.
Largest Contentful Paint (LCP) measures loading speed. How long does it take for the largest visible element to render? Target: under 2.5 seconds. Slow LCPs are usually caused by render-blocking JavaScript, large unoptimised images, or slow server response times.
Interaction to Next Paint (INP) measures interactivity. How quickly does the page respond when someone clicks, taps, or types? Target: under 200ms. A high INP is usually heavy JavaScript blocking the main thread.
Cumulative Layout Shift (CLS) measures visual stability. Does the page move unexpectedly while loading? Target: below 0.1. Layout shifts are caused by images without set dimensions, late-loading ads, or dynamically injected content.
Why do Core Web Vitals matter beyond rankings? Because they measure real friction. A page that shifts while someone is trying to tap a button loses the tap. A page that takes 4 seconds to load loses the visitor. A page that doesn't respond to input loses trust. Google is measuring what users already know and feel.
Most businesses do not know their Core Web Vitals scores. The businesses that do, and that consistently score in the "Good" range, have a compounding advantage: lower bounce rates, better rankings, and higher conversion rates. All from the same investment.
Measure your Core Web Vitals with Google PageSpeed Insights, Google Search Console, or Chrome DevTools. All three metrics must be in the "Good" range to pass the assessment. Custom Next.js sites consistently achieve this. WordPress sites with plugins often do not.