LCP measures when the largest content element in the viewport finishes rendering. On a landing page, that's usually the hero image or the main headline text block. Google considers LCP under 2.5 seconds "good," 2.5-4 seconds "needs improvement," and above 4 seconds "poor." Of the three Core Web Vitals, LCP correlates most directly with perceived load speed and conversion rates.
Think about it from the visitor's perspective: they click your ad, the browser starts loading, and LCP is the moment they can actually read your headline and see your hero image. Everything before that is waiting. Our data shows that pages with LCP under 2.5s convert at roughly 1.5x the rate of pages with LCP over 4s, controlling for other factors.
How to fix a slow LCP
First, identify your LCP element (Chrome DevTools > Performance > look for the LCP marker). If it's an image: optimize format (WebP/AVIF), preload it with <link rel="preload">, ensure it's not lazy-loaded (the hero image should load eagerly), and set explicit dimensions. If it's text: the bottleneck is usually render-blocking CSS or web font loading delays.
The counterintuitive fix: sometimes the fastest way to improve LCP is to make your hero image smaller (in viewport area), causing the LCP element to switch to your headline text — which renders faster than any image. Function over form. A fast-loading headline beats a slow-loading hero image every time.