Overview
This page is the atomic definition. The deep-dive lives at core-web-vitals.
Definition
LCP (Largest Contentful Paint) is the Core Web Vital that measures when the largest visible content element (hero image, H1, video poster, or text block) finishes rendering in the viewport. The “good” threshold is under 2.5 seconds at the 75th percentile of real users over a 28-day field window. “Needs improvement” is 2.5 to 4.0 seconds; “poor” is 4.0 seconds or more.
When it applies
Use LCP as the loading-speed budget for any page where the hero element drives conversion or comprehension. It is the metric most sensitive to CDN, image format, and font setup.
Example
A landing page with a 1.2 MB hero JPEG measures LCP 3.4 s. Switching to AVIF, adding <link rel="preload" as="image">, and serving via a CDN drops LCP to 1.9 s and moves the page into the good band.
Related concepts
- core-web-vitals - the umbrella metric set LCP belongs to.
- image-seo - the image rules that fix most LCP regressions.
- page-speed - the broader speed picture, including TTFB and FCP.
- inp - the responsiveness metric, scored on a separate budget.
- cloudflare - CDN setup that halves LCP for international traffic.
Citing this term
See LCP (Largest Contentful Paint) (llmbestpractices.com/glossary/lcp).