Introduction

Largest Contentful Paint (LCP) is a vital metric in Google's Core Web Vitals, reflecting how swiftly the main content of a page becomes visible to users. Achieving a strong LCP score (under 2.5 seconds) is essential for both user satisfaction and search engine optimization. In this article, you'll discover actionable methods to enhance LCP in your Next.js projects and consistently earn higher Lighthouse scores.

1. Optimize Images

Images frequently represent the largest elements on a webpage. Next.js offers the next/image component, which streamlines image optimization.

Leverage the next/image Component

Swap out traditional <img> tags for Next.js's Image component. This approach delivers automatic resizing, lazy loading, and support for modern formats like WebP.

Best Practices:

• Apply the priority prop to images that are immediately visible on page load.
• Always define width and height to maintain layout stability.
• Serve images in efficient formats (WebP/AVIF) whenever possible.

2. Reduce Render-Blocking Resources

CSS and JavaScript that block rendering can slow down LCP. While Next.js inlines critical CSS and enables code splitting by default, further improvements are possible:

Best Practices:

• Eliminate unused CSS and JavaScript.
• Utilize the next/script component with strategy="beforeInteractive" or strategy="lazyOnload" for third-party scripts.
• Use dynamic imports for components that aren't essential at first render.

3. Embrace Server-Side Rendering (SSR) or Static Generation

Next.js supports both SSR and Static Site Generation (SSG), which can significantly improve LCP by delivering pre-rendered HTML to users.

Best Practices:

• Implement getStaticProps or getServerSideProps for pages that rely on dynamic data.
• Favor SSG for content that remains relatively static.

4. Preload Critical Resources

Preloading essential assets such as fonts and above-the-fold images helps browsers prioritize what matters most.

Best Practices:

• Add <link rel="preload"> tags in your custom _document.js for fonts and key images.
• Be selective with preloading to avoid overwhelming the browser and degrading performance.

5. Continuously Monitor and Test

Regularly assess your site's performance using Lighthouse and WebPageTest. Take advantage of Next.js Analytics or the web-vitals library to track real user metrics and identify areas for improvement.

Conclusion

Boosting LCP in Next.js involves thoughtful image optimization, minimizing render-blocking resources, leveraging SSR or SSG, preloading vital assets, and ongoing performance monitoring. By adopting these strategies, you'll deliver faster load times, achieve superior Lighthouse scores, and provide an exceptional experience for your users.