LCP (Largest Contentful Paint) measures the time from when a page starts loading until the largest content element within the visible area (viewport), usually an image, video, or large block of text, is fully rendered.
Target values:
- Good: under 2.5 seconds
- Needs improvement: between 2.5 and 4.0 seconds
- Poor: over 4.0 seconds
Main factors that slow down LCP:
- Unoptimized large images
- Slow server response time (TTFB)
- Render-blocking JavaScript and CSS
- Delayed web font loading
- Slow third-party scripts
Tip: Identify your LCP element (Chrome DevTools > Performance) and use fetchpriority="high" and preload to prioritize it. If it is an image, convert it to WebP or AVIF format.