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# Upgrade Guide

# 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

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 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/ getServerSidePropshave 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 .babelrcon 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/imagenow 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.itemand 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 classNameprop 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 nginxyou 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.allto 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 targetin next.config.jsyou 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 targetoption set to serverlessplease 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: falseflag in next.config.js.

# PORT is now supported for next dev and next start

Next.js 11 supports the PORTenvironment variable to set the port the application has to run on. Using -p/--portis still recommended but if you were prohibited from using -pin any way you can now use PORTas 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-imagesor next-optimized-imagespackages you can either move to the new built-in support using next/imageor disable the feature:

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

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

The next/appcomponent's componentDidCatchhas 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.jshas a custom componentDidCatchmethod you can remove super.componentDidCatchas 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.jsimports Containerfrom next/appyou can remove Containeras 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/ getServerSidePropsthese 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 unsizedproperty on next/imagewas deprecated in Next.js 10.0.1. You can use layout="fill"instead. In Next.js 11 unsizedwas removed.

# Remove modules property on next/dynamic

The modulesand renderoption for next/dynamichave been deprecated since Next.js 9.5 showing a warning that it has been deprecated. This was done in order to make next/dynamicclose to React.lazyin API surface. In Next.js 11 the modulesand renderoptions 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 modulesand renderyou can refer to the documentation .

# Remove Head.rewind

Head.rewindhas 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: falseto next.config.jsif 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.eventsduring rendering, in Next.js 11 router.eventsis no longer provided during pre-rendering. Ensure you're accessing router.eventsin 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.eventswhich was an internal property that was not public please make sure to use router.eventsas 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 Reactvariable 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 Reactwithout 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 routesin your vercel.jsonfile 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.jsoncustomization.

You can read more about Dynamic Routing here .

# Check your Custom (pages/_app.js)

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

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

The following getInitialPropsdoes 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-typescriptand warn you to remove it. Please remove this plugin from your next.config.js.

Remove references to @zeit/next-typescript/babelfrom 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 nextpackage, so you need to uninstall @types/nextas 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 configfrom 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 configexport 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 loadingproperty:

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 withAmphigher-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.jswould 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.jswith 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/dynamicto be closer to React's implementation (React.lazyand 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
Last Updated: 5/13/2023, 8:55:38 PM

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