Next.js Dynamic Import vs React Lazy: What's the Difference?

Ibsen Valath

Updated on September 1, 2024

If you've been working with React or Next.js for a while, you've probably heard about “dynamic imports” and “lazy imports.” While both are powerful tools to optimize your app, they aren't exactly the same thing. Let's break it down in a simple way so you can decide which one to use and when.

Next.js takes the concept of dynamic imports to the next level (pun intended). Dynamic imports in Next.js allow you to load components on-demand, reducing the initial load time of your app. It's especially useful when you're working with large components or libraries that don't need to be loaded immediately. Here's what it might look like:


import dynamic from 'next/dynamic';

const HeavyComponent = dynamic(() => import('../components/HeavyComponent'));

export default function Home() {
  return (
    <div>
      <h1>Welcome to My App</h1>
      <HeavyComponent />
    </div>
  );

Server-Side Rendering (SSR) Support: You can decide if a component should be server-rendered or not by passing options. Custom Loading Component: You can specify a custom loading indicator to show while the component is being fetched. Error Handling: With proper configurations, you can handle errors more gracefully.React.lazy is a built-in React feature for code-splitting. It's straightforward and does what you'd expect: loads a component lazily when it's needed. Here's an example:


import React, { Suspense } from 'react';

const HeavyComponent = React.lazy(() => import('../components/HeavyComponent'));

export default function Home() {
  return (
    <div>
      <h1>Welcome to My App</h1>
      <Suspense fallback={<div>Loading...</div>}>
        <HeavyComponent />
      </Suspense>
    </div>
  );

Built into React: No extra imports or dependencies are required. Works with Suspense: You can show a fallback UI while waiting for the component to load. Simplicity: It's super straightforward for most use cases.While both tools achieve similar goals, there are some key differences:

Feature	Next.js Dynamic Import	React.lazy
Server-Side Rendering	Supported	Not supported
Custom Loading Component	Yes	No (uses Suspense instead)
Error Handling	More configurable	Requires wrapping with error boundaries
Flexibility	High (more options)	Simple and minimalistic

Use Next.js dynamic import when you're working in a Next.js project and need more control, like SSR or a custom loading state. It's tailored for the Next.js ecosystem and offers advanced features.Use React.lazy if you're building a pure React app or need a quick way to split code without worrying about SSR or additional configurations. Dynamic imports and lazy loading are essential tools for optimizing modern web apps. Next.js's dynamic import shines in flexibility and SSR support, while React.lazy is perfect for simple and straightforward lazy loading. Pick the one that fits your project's needs, and you'll be on your way to faster load times and a smoother user experience. Got a favorite or a question? Let me know!

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Next.js Dynamic Import vs React Lazy: What's the Difference?

Dynamic Imports in Next.js

Cool features of Next.js dynamic imports

React.lazy

What makes React.lazy great

Key Differences

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