Largest Contentful Paint (LCP)
How long it takes for the largest visible element to load.
LCP measures the render time of the largest image, video poster, or text block in the viewport during page load. It stops when that element is painted and stable enough to count. Slow LCP usually means late discovery (HTML depth), slow server TTFB, unoptimized hero media, or render-blocking CSS/JS in front of the hero.
Why developers care
LCP is the most actionable Core Web Vital for many marketing and app shells: you can often win hundreds of milliseconds with fetchpriority="high" on the hero, preloading the LCP image, shrinking image bytes, or moving blocking scripts. SpeedFixer ties failing Lighthouse audits to nginx or CDN snippets so you do not guess.
Example
<link rel="preload" as="image" href="/hero.webp" type="image/webp">
<img src="/hero.webp" alt="..." width="1200" height="630" fetchpriority="high">