How LCP differs from old speed metrics
Old metrics like "page load time" or "DOMContentLoaded" measured when the browser finished parsing — not when the visitor felt the page was ready. LCP fixes this by measuring perceived loading: when the largest visible element finally appears. Most visitors decide whether to stay or bounce based on this moment, not on full page load.
What element is your LCP?
Open Chrome DevTools → Lighthouse → Performance, run an audit, expand "Largest Contentful Paint." The element it names is what to optimize. On 80%+ of landing pages it's the hero image. The remaining 20% are split between hero video poster frames, hero text blocks, and (rarely) iframe embeds.
The fastest fix
If your LCP is an image: convert to WebP/AVIF, set explicit width/height, generate responsive srcset, and add <link rel="preload">. These four changes routinely cut LCP by 1–2 seconds. Full guide here. Test your LCP to see where you currently stand.