turbo

Turbopack can be customized to transform different files and change how modules are resolved.

Good to know:

• These features are experimental and will only work with next --turbo.
• Turbopack for Next.js does not require loaders nor loader configuration for built-in functionality. Turbopack has built-in support for css and compiling modern JavaScript, so there's no need for css-loader, postcss-loader, or babel-loader if you're using @babel/preset-env.

webpack loaders

If you need loader support beyond what's built in, many webpack loaders already work with Turbopack. There are currently some limitations:

• Only a core subset of the webpack loader API is implemented. Currently, there is enough coverage for some popular loaders, and we'll expand our API support in the future.
• Only loaders that return JavaScript code are supported. Loaders that transform files like stylesheets or images are not currently supported.
• Options passed to webpack loaders must be plain JavaScript primitives, objects, and arrays. For example, it's not possible to pass require()d plugin modules as option values.

To configure loaders, add the names of the loaders you've installed and any options in next.config.js, mapping file extensions to a list of loaders:

module.exports = {
  experimental: {
    turbo: {
      rules: {
        '*.svg': {
          loaders: ['@svgr/webpack'],
          as: '*.js',
        },
      },
    },
  },
}

Good to know: Prior to Next.js version 13.4.4, experimental.turbo.rules was named experimental.turbo.loaders and only accepted file extensions like .mdx instead of *.mdx.

Supported loaders

The following loaders have been tested to work with Turbopack's webpack loader implementation:

• babel-loader
• @svgr/webpack
• svg-inline-loader
• yaml-loader
• string-replace-loader
• raw-loader
• sass-loader

Resolve aliases

Through next.config.js, Turbopack can be configured to modify module resolution through aliases, similar to webpack's resolve.alias configuration.

To configure resolve aliases, map imported patterns to their new destination in next.config.js:

module.exports = {
  experimental: {
    turbo: {
      resolveAlias: {
        underscore: 'lodash',
        mocha: { browser: 'mocha/browser-entry.js' },
      },
    },
  },
}

This aliases imports of the underscore package to the lodash package. In other words, import underscore from 'underscore' will load the lodash module instead of underscore.

Turbopack also supports conditional aliasing through this field, similar to Node.js's conditional exports. At the moment only the browser condition is supported. In the case above, imports of the mocha module will be aliased to mocha/browser-entry.js when Turbopack targets browser environments.

Resolve extensions

Through next.config.js, Turbopack can be configured to resolve modules with custom extensions, similar to webpack's resolve.extensions configuration.

To configure resolve extensions, use the resolveExtensions field in next.config.js:

module.exports = {
  experimental: {
    turbo: {
      resolveExtensions: [
        '.mdx',
        '.tsx',
        '.ts',
        '.jsx',
        '.js',
        '.mjs',
        '.json',
      ],
    },
  },
}

This overwrites the original resolve extensions with the provided list. Make sure to include the default extensions.

For more information and guidance for how to migrate your app to Turbopack from webpack, see Turbopack's documentation on webpack compatibility.

Module ID strategy

Turbopack currently supports two strategies for assigning module IDs: 'named' and 'deterministic'.

'named' assigns readable module IDs based on the module's path and functionality.

'deterministic' assigns small hashed numeric module IDs, which are mostly consistent between builds and therefore help with long-term caching.

If not set, Turbopack will use 'named' for development builds and 'deterministic' for production builds.

To configure the module IDs strategy, use the moduleIdStrategy field in next.config.js:

module.exports = {
  experimental: {
    turbo: {
      moduleIdStrategy: 'deterministic',
    },
  },
}