LCP (Largest Contentful Paint) is a Core Web Vitals metric that measures how long it takes for the largest visible content element to render in the viewport.
The largest element is usually a hero image, a video poster frame, or a large block of text. LCP marks the point at which the main content of the page becomes visible, which is a good proxy for perceived load speed. A good LCP is 2.5 seconds or less, a value between 2.5 and 4 seconds needs improvement, and anything above 4 seconds is poor. These thresholds are measured at the 75th percentile of real visits across mobile and desktop.
Common causes of slow LCP include a slow server response, render-blocking CSS and JavaScript, slow-loading resources, and client-side rendering that delays the main element. Lazy loading the LCP element is a frequent self-inflicted mistake, since it pushes the most important paint later. Preloading the hero image, serving it in a modern format, and trimming render-blocking resources are the usual fixes.
The deep guide below covers field versus lab measurement and a full optimization workflow.
Related: LCP complete guide, Field vs lab data, INP
Claude Vincent is a technical SEO consultant focused on crawlability, rendering, and AI-search visibility. He writes the field guides and case studies at SEO ProCheck, with a bias toward the durable, unglamorous work that decides whether search engines and AI answer engines can actually read and cite a site.
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