How to improve page load speed in Next.js?

@virginie 

Improving page load speed in a Next.js application involves several strategies that focus on optimizing both the front end and the back end. Here are some effective techniques:

1. Code Splitting and Lazy Loading: Use dynamic imports to lazy load components. Next.js supports dynamic imports out of the box, which allows you to load components asynchronously when they are needed. import dynamic from 'next/dynamic'; const HeavyComponent = dynamic(() => import('../components/HeavyComponent'), { ssr: false });
2. Optimize Images: Utilize Next.js Image component which automatically optimizes your images. The component performs lazy loading by default and serves responsive images. import Image from 'next/image';
3. Implement Caching: Set caching policies using headers. You can configure caching in the next.config.js file or at your CDN layer to ensure static assets are cached efficiently.
4. Use a Content Delivery Network (CDN): Deploy your Next.js app on platforms providing CDN support (e.g., Vercel, Netlify) to ensure your static assets are served from locations closer to the users.
5. Optimize and Minimize Assets: Compress CSS, JavaScript, and HTML files. Next.js automatically supports CSS and JavaScript minification in production builds. Use plugins such as next-optimized-images to further optimize image delivery and file size.
6. Static Site Generation (SSG) and Incremental Static Regeneration (ISR): Use SSG to pre-render pages at build time, which can significantly reduce loading times for static content. Use ISR to update static content as needed without rebuilding your entire application.
7. Reduce JavaScript Payload: Identify and eliminate unused JavaScript. Use tools like Webpack Bundle Analyzer to analyze and optimize your JavaScript bundle size.
8. Prefetching and Preloading: Next.js supports automatic page prefetching in production. Additionally, you can use next/link with prefetch attributes to pre-load required resources.
9. Optimize Fonts: Use font-display: swap in your CSS to reduce render-blocking behavior. Leverage the next/font for automatic font optimizations.
10. Server-Side Rendering (SSR) vs Static Rendering: Depending on your needs, choose between SSR and SSG. Using SSR for dynamic content may optimize initial load times compared to client-side fetching.
11. Use React's Concurrent Features: Leverage React 18’s concurrent features, such as React Suspense and the experimental concurrent mode, for smoother UI rendering.

By incorporating these strategies, you can significantly enhance the performance of your Next.js applications, resulting in faster page load times and improved user experience.