What is Core Web Vitals?
Core Web Vitals are Google's set of specific metrics that measure real-world user experience: loading speed (LCP), interactivity (INP), and visual stability (CLS). They are a confirmed Google ranking factor.
LCP (Largest Contentful Paint): Measures when the largest visible element finishes loading. Target: under 2.5 seconds. Common fixes: optimize images, improve server response time, reduce render-blocking resources.
INP (Interaction to Next Paint): Measures responsiveness to user clicks, taps, and key presses. Target: under 200ms. Common fixes: break up long JavaScript tasks, optimize event handlers.
CLS (Cumulative Layout Shift): Measures unexpected layout movement. Target: under 0.1. Common fixes: set image dimensions, use font-display: swap, avoid injecting content above existing elements.
43% of websites fail INP. Passing all three CWV correlates with 24% lower bounce rates.
Example
A website hero image that takes 4 seconds to load fails LCP. Optimizing it with next/image, WebP format, and priority loading can bring it under 2 seconds.