LCP Optimization Strategies
1. Eliminate Resource Load Delay
Goal: Ensure the LCP resource starts loading as early as possible.
- Early Discovery: Ensure the LCP resource is discoverable in the initial HTML document response (not dynamically added by JS or hidden in
data-src). - Preload: Use
<link rel="preload">withfetchpriority="high"for critical images or fonts. - Avoid Lazy Loading: Never set
loading="lazy"on the LCP image. - Fetch Priority: Use
fetchpriority="high"on the<img>tag. - Same Origin: Host critical resources on the same origin or use
<link rel="preconnect">.
2. Eliminate Element Render Delay
Goal: Ensure the LCP element can render immediately after its resource has finished loading.
- Minimize Render-Blocking CSS: Inline critical CSS and defer non-critical CSS. Ensure the stylesheet is smaller than the LCP resource.
- Minimize Render-Blocking JS: Avoid synchronous scripts in the
<head>. Inline very small scripts. - Server-Side Rendering (SSR): Deliver the full HTML markup from the server so image resources are discoverable immediately.
- Break Up Long Tasks: Prevent large JavaScript tasks from blocking the main thread during rendering.
3. Reduce Resource Load Duration
Goal: Reduce the time spent transferring the bytes of the resource.
- Optimize Resource Size: Serve optimal image sizes, use modern formats (AVIF, WebP), and compress images/fonts.
- Geographic Proximity (CDN): Use a Content Delivery Network to get servers closer to users.
- Reduce Contention: Use
fetchpriority="high"to prevent lower-priority resources from competing for bandwidth. - Caching: Use efficient
Cache-Controlpolicies.
4. Reduce Time to First Byte (TTFB)
Goal: Deliver the initial HTML as quickly as possible.
- Minimize Redirects: Avoid multiple redirects from advertisements or shortened links.
- CDN Caching: Cache static HTML documents at the edge.
- Edge Computing: Move dynamic logic to the edge to avoid trips to the origin server.
- Back/Forward Cache: Ensure pages are eligible for bfcache.