Core Web Vitals are three metrics Google uses to measure how users experience your page. They're a confirmed ranking signal, and they directly correlate with conversion rates.
LCP (Largest Contentful Paint) — How fast the main content loads. Good: under 2.5s. Poor: over 4s. Usually your hero image or headline text. The metric with the strongest conversion correlation.
CLS (Cumulative Layout Shift) — How much things jump around while loading. Good: under 0.1. Poor: over 0.25. Caused by images without dimensions, late-loading fonts, and dynamic content injection. Destroys trust.
INP (Interaction to Next Paint) — How fast the page responds to clicks and taps. Good: under 200ms. Poor: over 500ms. Replaced FID in 2024. Affected by heavy JavaScript blocking the main thread.
The conversion connection
Google and Deloitte data shows each additional second of load time reduces conversions by 7-20%. But speed is one factor among many. A page that loads in 1 second with a terrible headline won't convert. A page that loads in 3 seconds with a perfect value proposition still might. Optimize Core Web Vitals to remove performance as a bottleneck, not as a silver bullet.