LCP — Largest Contentful Paint — is the Core Web Vital that measures how long it takes for the biggest visible element on a page to finish rendering, from the moment the user starts loading the URL. 'Biggest' usually means the hero image, a large heading, or the first block of text above the fold. Google's 'good' threshold is 2.5 seconds or less on a 28-day field-data rolling window; 'poor' starts at 4 seconds. LCP is the closest metric to how fast a page actually feels when it opens, which is why it replaced the older First Contentful Paint as the headline speed number in 2020. The most common causes of a failing LCP are unoptimised hero images, server response times over 500 milliseconds, render-blocking third-party scripts, and web fonts that block text paint. Fixing LCP usually means fixing the image pipeline first.
What a fast LCP looks like on a real build
On this site, the hero on the homepage hits LCP around 1.1 seconds on a mid-range Android. The image uses Next.js's Image component with priority, an explicit width and height, and is served as AVIF with a WebP fallback. The server — Vercel's edge network — responds in under 100 milliseconds. No render-blocking scripts above the fold. A typical Squarespace hero on the same device lands around 3 to 4 seconds because the platform injects analytics and ad scripts before the image can paint.
Why every extra second hurts bounce
Every additional second of LCP measurably increases bounce. Google's own research shows sites with LCP under 2.5s have roughly 24% lower bounce rates than sites above 4s. For a small business, that is the difference between a Google Ads click turning into an enquiry and the same click abandoning the page before the hero has even rendered. Paid traffic is especially unforgiving of slow LCP — the user arrived with intent, but patience does not come free.
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