Upgrade Guide

Upgrading to 12.2

If you were using Middleware prior to 12.2, please see the upgrade guide for more information.

Upgrading from 11 to 12

Minimum Node.js version

The minimum Node.js version has been bumped from 12.0.0 to 12.22.0 which is the first version of Node.js with native ES Modules support.

Upgrade React version to latest

The minimum required React version is 17.0.2. To upgrade you can run the following command in the terminal:

npm install react@latest react-dom@latest

Or using yarn:

yarn add react@latest react-dom@latest

Upgrade Next.js version to 12

To upgrade you can run the following command in the terminal:

npm install next@12

or

yarn add next@12

SWC replacing Babel

Next.js now uses Rust-based compiler SWC to compile JavaScript/TypeScript. This new compiler is up to 17x faster than Babel when compiling individual files and up to 5x faster Fast Refresh.

Next.js provides full backwards compatibility with applications that have custom Babel configuration. All transformations that Next.js handles by default like styled-jsx and tree-shaking of getStaticProps / getStaticPaths / getServerSideProps have been ported to Rust.

When an application has a custom Babel configuration, Next.js will automatically opt-out of using SWC for compiling JavaScript/Typescript and will fall back to using Babel in the same way that it was used in Next.js 11.

Many of the integrations with external libraries that currently require custom Babel transformations will be ported to Rust-based SWC transforms in the near future. These include but are not limited to:

• Styled Components
• Emotion
• Relay

In order to prioritize transforms that will help you adopt SWC, please provide your .babelrc on the feedback thread.

SWC replacing Terser for minification

You can opt-in to replacing Terser with SWC for minifying JavaScript up to 7x faster using a flag in next.config.js:

module.exports = {
  swcMinify: true,
}

Minification using SWC is an opt-in flag to ensure it can be tested against more real-world Next.js applications before it becomes the default in Next.js 12.1. If you have feedback about minification, please leave it on the feedback thread.

Improvements to styled-jsx CSS parsing

On top of the Rust-based compiler we've implemented a new CSS parser based on the CSS parser that was used for the styled-jsx Babel transform. This new parser has improved handling of CSS and now errors when invalid CSS is used that would previously slip through and cause unexpected behavior.

Because of this change invalid CSS will throw an error during development and next build. This change only affects styled-jsx usage.

next/image changed wrapping element

next/image now renders the <img> inside a <span> instead of <div>.

If your application has specific CSS targeting span, for example .container span, upgrading to Next.js 12 might incorrectly match the wrapping element inside the <Image> component. You can avoid this by restricting the selector to a specific class such as .container span.item and updating the relevant component with that className, such as <span className="item" />.

If your application has specific CSS targeting the next/image <div> tag, for example .container div, it may not match anymore. You can update the selector .container span, or preferably, add a new <div className="wrapper"> wrapping the <Image> component and target that instead such as .container .wrapper.

The className prop is unchanged and will still be passed to the underlying <img> element.

See the documentation for more info.

Next.js' HMR connection now uses a WebSocket

Previously, Next.js used a server-sent events connection to receive HMR events. Next.js 12 now uses a WebSocket connection.

In some cases when proxying requests to the Next.js dev server, you will need to ensure the upgrade request is handled correctly. For example, in nginx you would need to add the following configuration:

location /_next/webpack-hmr {
    proxy_pass http://localhost:3000/_next/webpack-hmr;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}

For custom servers, such as express, you may need to use app.all to ensure the request is passed correctly, for example:

app.all('/_next/webpack-hmr', (req, res) => {
  nextjsRequestHandler(req, res)
})

Webpack 4 support has been removed

If you are already using webpack 5 you can skip this section.

Next.js has adopted webpack 5 as the default for compilation in Next.js 11. As communicated in the webpack 5 upgrading documentation Next.js 12 removes support for webpack 4.

If your application is still using webpack 4 using the opt-out flag you will now see an error linking to the webpack 5 upgrading documentation.

target option deprecated

If you do not have target in next.config.js you can skip this section.

The target option has been deprecated in favor of built-in support for tracing what dependencies are needed to run a page.

During next build, Next.js will automatically trace each page and its dependencies to determine all of the files that are needed for deploying a production version of your application.

If you are currently using the target option set to serverless please read the documentation on how to leverage the new output.

Upgrading from version 10 to 11

Upgrade React version to latest

Most applications already use the latest version of React, with Next.js 11 the minimum React version has been updated to 17.0.2.

To upgrade you can run the following command:

npm install react@latest react-dom@latest

Or using yarn:

yarn add react@latest react-dom@latest

Upgrade Next.js version to 11

To upgrade you can run the following command in the terminal:

npm install next@11

or

yarn add next@11

Webpack 5

Webpack 5 is now the default for all Next.js applications. If you did not have custom webpack configuration your application is already using webpack 5. If you do have custom webpack configuration you can refer to the Next.js webpack 5 documentation for upgrading guidance.

Cleaning the distDir is now a default

The build output directory (defaults to .next) is now cleared by default except for the Next.js caches. You can refer to the cleaning distDir RFC for more information.

If your application was relying on this behavior previously you can disable the new default behavior by adding the cleanDistDir: false flag in next.config.js.

PORT is now supported for next dev and next start

Next.js 11 supports the PORT environment variable to set the port the application has to run on. Using -p/--port is still recommended but if you were prohibited from using -p in any way you can now use PORT as an alternative:

Example:

PORT=4000 next start

next.config.js customization to import images

Next.js 11 supports static image imports with next/image. This new feature relies on being able to process image imports. If you previously added the next-images or next-optimized-images packages you can either move to the new built-in support using next/image or disable the feature:

module.exports = {
  images: {
    disableStaticImages: true,
  },
}

Remove super.componentDidCatch() from pages/_app.js

The next/app component's componentDidCatch has been deprecated since Next.js 9 as it's no longer needed and has since been a no-op, in Next.js 11 it has been removed.

If your pages/_app.js has a custom componentDidCatch method you can remove super.componentDidCatch as it is no longer needed.

Remove Container from pages/_app.js

This export has been deprecated since Next.js 9 as it's no longer needed and has since been a no-op with a warning during development. In Next.js 11 it has been removed.

If your pages/_app.js imports Container from next/app you can remove Container as it has been removed. Learn more in the documentation.

Remove props.url usage from page components

This property has been deprecated since Next.js 4 and has since shown a warning during development. With the introduction of getStaticProps / getServerSideProps these methods already disallowed usage of props.url. In Next.js 11 it has been removed completely.

You can learn more in the documentation.

Remove unsized property on next/image

The unsized property on next/image was deprecated in Next.js 10.0.1. You can use layout="fill" instead. In Next.js 11 unsized was removed.

Remove modules property on next/dynamic

The modules and render option for next/dynamic have been deprecated since Next.js 9.5 showing a warning that it has been deprecated. This was done in order to make next/dynamic close to React.lazy in API surface. In Next.js 11 the modules and render options have been removed.

This option hasn't been mentioned in the documentation since Next.js 8 so it's less likely that your application is using it.

If your application does use modules and render you can refer to the documentation.

Remove Head.rewind

Head.rewind has been a no-op since Next.js 9.5, in Next.js 11 it was removed. You can safely remove your usage of Head.rewind.

Moment.js locales excluded by default

Moment.js includes translations for a lot of locales by default. Next.js now automatically excludes these locales by default to optimize bundle size for applications using Moment.js.

To load a specific locale use this snippet:

import moment from 'moment'
import 'moment/locale/ja'

moment.locale('ja')

You can opt-out of this new default by adding excludeDefaultMomentLocales: false to next.config.js if you do not want the new behavior, do note it's highly recommended to not disable this new optimization as it significantly reduces the size of Moment.js.

Update usage of router.events

In case you're accessing router.events during rendering, in Next.js 11 router.events is no longer provided during pre-rendering. Ensure you're accessing router.events in useEffect:

useEffect(() => {
  const handleRouteChange = (url, { shallow }) => {
    console.log(
      `App is changing to ${url} ${
        shallow ? 'with' : 'without'
      } shallow routing`
    )
  }

  router.events.on('routeChangeStart', handleRouteChange)

  // If the component is unmounted, unsubscribe
  // from the event with the `off` method:
  return () => {
    router.events.off('routeChangeStart', handleRouteChange)
  }
}, [router])

If your application uses router.router.events which was an internal property that was not public please make sure to use router.events as well.

React 16 to 17

React 17 introduced a new JSX Transform that brings a long-time Next.js feature to the wider React ecosystem: Not having to import React from 'react' when using JSX. When using React 17 Next.js will automatically use the new transform. This transform does not make the React variable global, which was an unintended side-effect of the previous Next.js implementation. A codemod is available to automatically fix cases where you accidentally used React without importing it.

Upgrading from version 9 to 10

There were no breaking changes between version 9 and 10.

To upgrade run the following command:

npm install next@10

Or using yarn:

yarn add next@10

Upgrading from version 8 to 9

Preamble

Production Deployment on Vercel

If you previously configured routes in your vercel.json file for dynamic routes, these rules can be removed when leveraging Next.js 9's new Dynamic Routing feature.

Next.js 9's dynamic routes are automatically configured on Vercel and do not require any vercel.json customization.

You can read more about Dynamic Routing here.

Check your Custom <App> (pages/_app.js)

If you previously copied the Custom <App> example, you may be able to remove your getInitialProps.

Removing getInitialProps from pages/_app.js (when possible) is important to leverage new Next.js features!

The following getInitialProps does nothing and may be removed:

class MyApp extends App {
  // Remove me, I do nothing!
  static async getInitialProps({ Component, ctx }) {
    let pageProps = {}

    if (Component.getInitialProps) {
      pageProps = await Component.getInitialProps(ctx)
    }

    return { pageProps }
  }

  render() {
    // ... etc
  }
}

Breaking Changes

@zeit/next-typescript is no longer necessary

Next.js will now ignore usage @zeit/next-typescript and warn you to remove it. Please remove this plugin from your next.config.js.

Remove references to @zeit/next-typescript/babel from your custom .babelrc (if present).

Usage of fork-ts-checker-webpack-plugin should also be removed from your next.config.js.

TypeScript Definitions are published with the next package, so you need to uninstall @types/next as they would conflict.

The following types are different:

This list was created by the community to help you upgrade, if you find other differences please send a pull-request to this list to help other users.

From:

import { NextContext } from 'next'
import { NextAppContext, DefaultAppIProps } from 'next/app'
import { NextDocumentContext, DefaultDocumentIProps } from 'next/document'

to

import { NextPageContext } from 'next'
import { AppContext, AppInitialProps } from 'next/app'
import { DocumentContext, DocumentInitialProps } from 'next/document'

The config key is now an export on a page

You may no longer export a custom variable named config from a page (i.e. export { config } / export const config ...). This exported variable is now used to specify page-level Next.js configuration like Opt-in AMP and API Route features.

You must rename a non-Next.js-purposed config export to something different.

next/dynamic no longer renders "loading..." by default while loading

Dynamic components will not render anything by default while loading. You can still customize this behavior by setting the loading property:

import dynamic from 'next/dynamic'

const DynamicComponentWithCustomLoading = dynamic(
  () => import('../components/hello2'),
  {
    loading: () => <p>Loading</p>,
  }
)

withAmp has been removed in favor of an exported configuration object

Next.js now has the concept of page-level configuration, so the withAmp higher-order component has been removed for consistency.

This change can be automatically migrated by running the following commands in the root of your Next.js project:

curl -L https://github.com/vercel/next-codemod/archive/master.tar.gz | tar -xz --strip=2 next-codemod-master/transforms/withamp-to-config.js npx jscodeshift -t ./withamp-to-config.js pages/**/*.js

To perform this migration by hand, or view what the codemod will produce, see below:

Before

import { withAmp } from 'next/amp'

function Home() {
  return <h1>My AMP Page</h1>
}

export default withAmp(Home)
// or
export default withAmp(Home, { hybrid: true })

After

export default function Home() {
  return <h1>My AMP Page</h1>
}

export const config = {
  amp: true,
  // or
  amp: 'hybrid',
}

next export no longer exports pages as index.html

Previously, exporting pages/about.js would result in out/about/index.html. This behavior has been changed to result in out/about.html.

You can revert to the previous behavior by creating a next.config.js with the following content:

// next.config.js
module.exports = {
  trailingSlash: true,
}

./pages/api/ is treated differently

Pages in ./pages/api/ are now considered API Routes. Pages in this directory will no longer contain a client-side bundle.

Deprecated Features

next/dynamic has deprecated loading multiple modules at once

The ability to load multiple modules at once has been deprecated in next/dynamic to be closer to React's implementation (React.lazy and Suspense).

Updating code that relies on this behavior is relatively straightforward! We've provided an example of a before/after to help you migrate your application:

Before

import dynamic from 'next/dynamic'

const HelloBundle = dynamic({
  modules: () => {
    const components = {
      Hello1: () => import('../components/hello1').then((m) => m.default),
      Hello2: () => import('../components/hello2').then((m) => m.default),
    }

    return components
  },
  render: (props, { Hello1, Hello2 }) => (
    <div>
      <h1>{props.title}</h1>
      <Hello1 />
      <Hello2 />
    </div>
  ),
})

function DynamicBundle() {
  return <HelloBundle title="Dynamic Bundle" />
}

export default DynamicBundle

After

import dynamic from 'next/dynamic'

const Hello1 = dynamic(() => import('../components/hello1'))
const Hello2 = dynamic(() => import('../components/hello2'))

function HelloBundle({ title }) {
  return (
    <div>
      <h1>{title}</h1>
      <Hello1 />
      <Hello2 />
    </div>
  )
}

function DynamicBundle() {
  return <HelloBundle title="Dynamic Bundle" />
}

export default DynamicBundle