Largest Contentful Paint (LCP) is one of three Core Web Vitals metrics, measuring the time from page navigation to when the largest visible content element (above the fold) finishes rendering. The "largest content" is usually the hero image, headline, or main video frame.
The 2026 thresholds are: under 2.5 seconds = good, 2.5-4.0 seconds = needs improvement, over 4.0 seconds = poor. Google uses LCP as a ranking signal in both classic search and AI Overviews source candidacy. Pages with poor LCP get demoted in ranking even when their content is otherwise strong.
The most common LCP problems are large unoptimized hero images (no WebP/AVIF format, no responsive sizing), render-blocking JavaScript that delays the largest element, slow Time to First Byte that pushes back the entire timeline, and lazy-loaded above-the-fold images (which are never lazy by best practice).
For AEO, LCP also affects AI crawler behavior. PerplexityBot, OAI-SearchBot, and ClaudeBot all have tighter response-time budgets than Googlebot — pages with slow LCP get crawled less frequently and ranked lower in AI-citation candidacy. Optimizing LCP lifts both classic SEO rank and AEO citation share.