This guide will help you understand how to transition from an existing non-ejected Create React App project to Next.js. Migrating to Next.js will allow you to:
And more! Let’s walk through a series of steps to complete the migration.
package.json and dependenciesThe first step towards migrating to Next.js is to update package.json and dependencies. You should:
react-scripts (but keep react and react-dom). If you're using React Router, you can also remove react-router-dom.next.scripts. One is next dev, which runs a development server at localhost:3000. You should also add next build and next start for creating and starting a production build.Here's an example package.json:
{
"scripts": {
"dev": "next dev",
"build": "next build",
"start": "next start"
},
"dependencies": {
"next": "latest",
"react": "latest",
"react-dom": "latest"
}
}
Create React App uses the public directory for the entry HTML file, whereas Next.js uses it for static assets. It's possible to add static assets here, but Create React App recommends importing them directly from JavaScript files.
public.index.html (the entry point of your application) to Next.js. Any <head> code should be moved to a custom _document.js. Any shared layout between all pages should be moved to a custom _app.js..next to .gitignore.With Create React App, you're likely using React Router. Instead of using a third-party library, Next.js includes its own file-system based routing.
Route components to new files in the pages directory./blog/:slug), you can use Dynamic Routes with Next.js (e.g. pages/blog/[slug].js). The value of slug is accessible through a query parameter. For example, the route /blog/first-post would forward the query object { 'slug': 'first-post' } to pages/blog/[slug].js (learn more here).For more information, see Migrating from React Router.
Next.js has built-in support for CSS, Sass and CSS-in-JS.
With Create React App, you can import .css files directly inside React components. Next.js allows you to do the same, but requires these files to be CSS Modules. For global styles, you'll need a custom _app.js to add a global stylesheet.
With client-side rendered applications (like Create React App), you can access window, localStorage, navigator, and other Web APIs out of the box.
Since Next.js uses pre-rendering, you'll need to safely access those Web APIs only when you're on the client-side. For example, the following code snippet will allow access to window only on the client-side.
if (typeof window !== 'undefined') {
// You now have access to `window`
}
A recommended way of accessing Web APIs safely is by using the useEffect hook, which only executes client-side:
import { useEffect } from 'react'
useEffect(() => {
// You now have access to `window`
}, [])
Since version 10.0.0, Next.js has a built-in Image Component and Automatic Image Optimization.
The Next.js Image Component, next/image, is an extension of the HTML <img> element, evolved for the modern web.
The Automatic Image Optimization allows for resizing, optimizing, and serving images in modern formats like WebP when the browser supports it. This avoids shipping large images to devices with a smaller viewport. It also allows Next.js to automatically adopt future image formats and serve them to browsers that support those formats.
Instead of optimizing images at build time, Next.js optimizes images on-demand, as users request them. Your build times aren't increased, whether shipping 10 images or 10 million images.
import Image from 'next/image'
export default function Home() {
return (
<>
<h1>My Homepage</h1>
<Image
src="/me.png"
alt="Picture of the author"
width={500}
height={500}
/>
<p>Welcome to my homepage!</p>
</>
)
}
Next.js has support for .env Environment Variables similar to Create React App. The main different is the prefix used to expose environment variables on the client-side.
REACT_APP_ prefix to NEXT_PUBLIC_.Most Create React App examples use react-helmet to assist with adding meta tags for proper SEO. With Next.js, we use next/head to add meta tags to your <head /> element. For example, here's an SEO component with Create React App:
// src/components/seo.js
import { Helmet } from 'react-helmet'
export default function SEO({ description, title, siteTitle }) {
return (
<Helmet
title={title}
titleTemplate={siteTitle ? `%s | ${siteTitle}` : null}
meta={[
{
name: `description`,
content: description,
},
{
property: `og:title`,
content: title,
},
{
property: `og:description`,
content: description,
},
{
property: `og:type`,
content: `website`,
},
{
name: `twitter:card`,
content: `summary`,
},
{
name: `twitter:creator`,
content: twitter,
},
{
name: `twitter:title`,
content: title,
},
{
name: `twitter:description`,
content: description,
},
]}
/>
)
}
And here's the same example using Next.js.
// src/components/seo.js
import Head from 'next/head'
export default function SEO({ description, title, siteTitle }) {
return (
<Head>
<title>{`${title} | ${siteTitle}`}</title>
<meta name="description" content={description} />
<meta property="og:type" content="website" />
<meta property="og:title" content={title} />
<meta property="og:description" content={description} />
<meta property="og:site_name" content={siteTitle} />
<meta property="twitter:card" content="summary" />
<meta property="twitter:creator" content={config.social.twitter} />
<meta property="twitter:title" content={title} />
<meta property="twitter:description" content={description} />
</Head>
)
}
If you want to move your existing Create React App to Next.js and keep a Single-Page App, you can move your old application's entry point to an Optional Catch-All Route named pages/[[...app]].js.
// pages/[[...app]].js
import { useState, useEffect } from 'react'
import CreateReactAppEntryPoint from '../components/app'
function App() {
const [isMounted, setIsMounted] = useState(false)
useEffect(() => {
setIsMounted(true)
}, [])
if (!isMounted) {
return null
}
return <CreateReactAppEntryPoint />
}
export default App
If you've ejected Create React App, here are some things to consider:
You can learn more about Next.js by completing our starter tutorial. If you have questions or if this guide didn't work for you, feel free to reach out to our community on GitHub Discussions.