Largest Contentful Paint (LCP) is a Core Web Vitals metric that measures the render time of the largest image, video, or text block visible within the user's viewport when the page first loads. LCP is Google's primary measure of perceived loading performance — the moment when the main content of a page has loaded and is visible to the user. A good LCP score means users see the most important content quickly, reducing the perception of slowness.

LCP Thresholds and Scoring

Google defines LCP performance in three tiers. A "Good" LCP score is 2.5 seconds or less — the page's largest content element renders within 2.5 seconds of the user initiating navigation. "Needs Improvement" is between 2.5 and 4.0 seconds. "Poor" is over 4.0 seconds. Google measures LCP using field data (real Chrome user experiences collected through CrUX) at the 75th percentile — meaning 75% of page loads must meet the threshold for the page to be classified in that tier. LCP can be measured using PageSpeed Insights, Lighthouse, or the Chrome DevTools Performance panel.

Key point: The LCP element is typically a hero image, above-the-fold banner, or the largest text block visible in the initial viewport. Identifying which element is your LCP before optimizing is crucial — PageSpeed Insights clearly identifies it in its report.

Common Causes of Slow LCP

Poor LCP scores are typically caused by slow resource loading chains:

  • Large, uncompressed images (the most common cause)
  • Render-blocking JavaScript or CSS that delays page rendering
  • Slow server response times (high Time to First Byte)
  • LCP element loaded lazily when it should be eagerly loaded
  • No preloading of the LCP image with a <link rel="preload"> tag

Why It Matters for SEO

LCP is the Core Web Vitals metric most directly related to perceived page speed — the user's experience of how fast a page loads. It is a ranking signal in Google's Page Experience system, and pages with poor LCP scores may rank lower than otherwise comparable pages with better performance. Beyond rankings, faster LCP directly reduces bounce rates and improves conversion rates. Optimizing LCP — primarily by compressing and properly sizing images, eliminating render-blocking resources, and improving server response time — is one of the highest-impact technical SEO improvements available for most websites.