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Webpack 5 Adoption

errors/webpack5.mdx

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Why This Message Occurred

Next.js has adopted webpack 5 as the default for compilation. We've spent a lot of effort into ensuring the transition from webpack 4 to 5 will be as smooth as possible.

Your application currently has webpack 5 disabled using the webpack5: false flag which has been removed in Next.js 12:

js
module.exports = {
  // Webpack 5 is enabled by default
  // You can still use webpack 4 while upgrading to the latest version of Next.js by adding the "webpack5: false" flag
  webpack5: false,
}

Using webpack 5 in your application has many benefits, notably:

  • Improved Disk Caching: next build is significantly faster on subsequent builds
  • Improved Fast Refresh: Fast Refresh work is prioritized
  • Improved Long Term Caching of Assets: Deterministic code output that is less likely to change between builds
  • Improved Tree Shaking
  • Support for assets using new URL("file.png", import.meta.url)
  • Support for web workers using new Worker(new URL("worker.js", import.meta.url))
  • Support for exports/imports field in package.json

In the past releases we have gradually rolled out webpack 5 to Next.js applications:

  • In Next.js 10.2 we automatically opted-in applications without custom webpack configuration in next.config.js
  • In Next.js 10.2 we automatically opted-in applications that do not have a next.config.js
  • In Next.js 11 webpack 5 was enabled by default for all applications. You could still opt-out and use webpack 4 to help with backwards compatibility using webpack5: false in next.config.js
  • In Next.js 12 webpack 4 support was removed.

Custom webpack configuration

In case you do have custom webpack configuration, either through custom plugins or your own modifications you'll have to take a few steps to ensure your applications works with webpack 5.

  • When using next-transpile-modules make sure you use the latest version which includes this patch
  • When using @zeit/next-css / @zeit/next-sass make sure you use the built-in CSS/Sass support instead
  • When using @zeit/next-preact use this example instead
  • When using @zeit/next-source-maps use the built-in production Source Map support
  • When using webpack plugins make sure they're upgraded to the latest version, in most cases the latest version will include webpack 5 support. In some cases these upgraded webpack plugins will only support webpack 5.

In case you're running into issues you can connect with the community in this help discussion.