Glossary
LCP (Largest Contentful Paint)
LCP is the time it takes for the largest visible element on a webpage to render. It's one of Google's three Core Web Vitals.
Largest Contentful Paint (LCP) measures when the largest above-the-fold element — usually a hero image, a hero video, or a headline — finishes rendering. It's a proxy for perceived load speed.
Google's threshold: LCP under 2.5 seconds is 'good', 2.5–4.0 is 'needs improvement', and over 4.0 is 'poor'.
Common LCP killers: heavy hero images that aren't optimized, hero videos without poster frames, render-blocking CSS, and slow server response times.
Example
Compressing a 4MB hero image down to 280KB and serving it via next/image with a priority hint can drop LCP from 3.8s to 1.2s.