Definition
LCP marks the moment the hero image or headline finishes loading. It anchors Core Web Vitals because users judge speed by when content appears, not when spinners stop. Slow servers, oversized heroes and render-blocking fonts are the usual culprits.
Why it matters
Sub-2.5s LCP correlates directly with conversion - every second of delay taxes every campaign you will ever run.
Formula
75th percentile load of the largest element
Benchmarks
Under 2.5s good; over 4s poor
All glossary terms