By Shad Super in Questions —

What Are the Most Common Issues That Cause Poor Largest Contentful Paint (LCP) Performance, and How Can I Resolve Them?

Overview

Largest Contentful Paint (LCP) marks the point during page load when the primary or "largest" content has painted. A low LCP measurement offers users a swift perception of a site's performance. Factors that negatively affect LCP include slow server response times, render-blocking JavaScript and CSS, slow resource load times, and client-side rendering. Mitigating these issues can significantly improve LCP.

1. Improving Server Response Times

Ensure Effective CDN Utilization

Employing a Content Delivery Network (CDN) helps to reduce the server response times by serving static resources from servers that are geographically near users' location, thereby decreasing latency. It can markedly speed up the loading time of the largest contentful paint [CDN Performance, 2021].

Capitalize on Server Caching

Server-side caching is a potent tool in improving server response times. By pre-rendering pages or components, you can drastically reduce the need for server-side computations, slashing the time taken to respond to user requests [HTTP Caching, 2022].

2. Efficient Resource Loading

Preload Key Assets

Preloading vital resources using the <link rel="preload"> can speed up load times by instructing the browser to download important resources without executing them [Preloading content, 2021].

Optimize Image Delivery

Images often constitute the LCP element, making their optimization crucial. Employing image compression techniques and Responsive Images (using the <srcset> and <sizes> attributes) can significantly reduce the load times of images [Serve Responsive Images, 2022].

3. Minimize Render-Blocking JavaScript and CSS

Critical CSS and JavaScript

Render-blocking resources halt the page render until they are downloaded and processed. Minifying CSS and JavaScript, inlining essential CSS and JavaScript, and deferring non-critical JavaScript and CSS can significantly reduce their impact on page load and LCP [Eliminate render-blocking resources, 2021].

4. Optimize Client-Side Rendering

Server-Side Rendering (SSR) or Static Generation (SG)

Client-side rendering can negatively impact LCP as it involves JavaScript execution that can delay the rendering of the largest contentful paint. Utilizing Server-Side Rendering (SSR) or Static Generation (SG) can mitigate this issue as they produce ready-to-render HTML that can quickly paint the largest contentful element [Render and commit, 2023].

Conclusion

Improving LCP involves a multi-faceted approach including optimizing server response times, efficient loading of images and critical resources, reducing the impact of render-blocking JavaScript and CSS, and optimizing client-side rendering. By correctly implementing these strategies, you can enhance the LCP performance significantly.

References