ReactJS
Next.js Dynamic Loading: Reduce Bundle Size & Improve Performance
Next.js, a framework for React, enhances performance by features such as dynamic imports, code splitting and dynamic routing. Of these, dynamic loading efficiently reduces first-load times and minimizes the bundle size.
What is Dynamic Loading?
Dynamic loading or lazy loading or code splitting, enables us to load modules or components only when required. What this implies is that rather than bundling everything together in advance, JavaScript loads only what is required, lowering the initial load time of the page and improving performance.
Key Benefits of Dynamic Loading:
- Reduces initial page load time
- Optimizes performance for large applications
- Decreases JavaScript bundle size
- Improves SEO & Core Web Vitals
- Enhances user experience by loading elements on demand
How to Implement Dynamic Loading in NextJS
Next.js provides built-in support for dynamic imports using next/dynamic. Let's look at some use cases where dynamic loading is beneficial.
1. Lazy Loading Components with next/dynamic
We can load components dynamically to reduce the initial bundle size.
import dynamic from 'next/dynamic';const HeavyComponent = dynamic(() => import('../components/HeavyComponent'), { ssr: false, // Avoid rendering on the server loading: () => <p>Loading...</p>, // Show a fallback while loading});export default function Page() { return <HeavyComponent />;}
Best Use Cases:
Large UI components (e.g., charts, maps, video players)
Third-party libraries (e.g., moment.js, Lodash)
2. Dynamic Route Loading
Next.js allows us to load pages dynamically using dynamic routes.
export async function getServerSideProps(params) { const data = await fetch(`https://api.example.com/post/${params.id}`); return { props: { data } };}
Best Use Cases:
Blog posts
Product details pages
User profiles
3. Client-Only Dynamic Components
Some components require browser-specific APIs (like window or localStorage). To prevent SSR errors, we can disable SSR for such components.
const ClientOnlyComponent = dynamic(() => import('../components/ClientOnlyComponent'), { ssr: false });
Best Use Cases:
Components that rely on localStorage, sessionStorage, or window
Animation libraries that depend on the browser
4. Lazy Loading Images with next/image
Instead of loading all images immediately, use the next/image component for lazy loading.
import Image from 'next/image';<Image src="/large-image.jpg" width={800} height={600} placeholder="blur" alt="Dynamic Image" />
Best Use Cases:
High-resolution images
Background images
Large media files
5. On-Demand Component Rendering Based on User Interaction
Sometimes, we only want to load a component when a user interacts with it.
const DynamicModal = dynamic(() => import('./Modal'), { ssr: false });function Page() { const [showModal, setShowModal] = useState(false); return ( <> <button onClick={() => setShowModal(true)}>Open Modal</button> {showModal && <DynamicModal />} </> );}
Best Use Cases:
Modals & popups
Sidebars & off canvas menus
Accordions & expandable content
Best Practices for Dynamic Loading
- Use next/dynamic for large components to improve performance.
- Disable SSR (ssr: false) for client only features.
- Provide a loading fallback to enhance user experience.
- Lazy-load third-party libraries to reduce the main bundle size.
- Monitor performance using Lighthouse & Chrome DevTools.
Conclusion
Dynamic loading in Next.js is a high performance optimization method that improves page speed and user experience by loading resources only when needed. Whether components, routes, images or third party libraries, strategically applying lazy loading strategically can make your Next.js apps faster and more efficient.
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