Largest Contentful Paint (LCP)
Also known as: lcp, lcp core web vital, largest contentful paint
Largest Contentful Paint (LCP) is a Core Web Vital that measures how long the largest visible content element (usually a hero image or heading) takes to render. A "good" LCP is 2.5 seconds or less at the 75th percentile.
- A "good" LCP is 2.5 seconds or less, measured at the 75th percentile of real visits.
- The LCP element is usually a hero image, so image weight dominates the score.
- Compressing images and using WebP/AVIF plus srcset is the highest-leverage fix.
What LCP measures
LCP reports the render time of the largest image, video poster, or block-level text element visible in the viewport during page load. It is timed relative to when the page first starts loading, and it captures the moment the main content is likely usable to the visitor.
Google's thresholds are 2.5 seconds or less = good, 2.5 to 4 seconds = needs improvement, and over 4 seconds = poor. Scores are taken at the 75th percentile of real visits via the Chrome User Experience Report.
What slows LCP down
On most pages the LCP element is an image, so image weight is the dominant factor. Slow server response (TTFB), render-blocking CSS and JavaScript, and client-side rendering all delay it. A large, uncompressed hero image is the single most common cause of a failing LCP.
Fixes include compressing and right-sizing images with responsive images (srcset), serving modern formats like WebP or AVIF, preloading the LCP image, and avoiding lazy-loading the hero (lazy load only below-the-fold media).
Why image optimization is the lever
Because the LCP element is so often a photo, image compression is the fastest way to move the metric. Cutting a hero from megabytes to kilobytes can pull LCP under the 2.5-second bar without any layout changes.
This mirrors what Cleanor does on a phone — finding the heavy, oversized media that bloats storage. On the web, the same oversized images are also what bloat your landing-page LCP.