Resolve

These options change how modules are resolved. Webpack provides reasonable defaults, but it is possible to change the resolving in detail. Have a look at Module Resolution for more explanation of how the resolver works.

resolve

object

Configure how modules are resolved. For example, when calling import 'lodash' in ES2015, the resolve options can change where webpack goes to look for 'lodash' (see modules).

webpack.config.js

module.exports = {
  //...
  resolve: {
    // configuration options
  },
};

resolve.alias

object

Create aliases to import or require certain modules more easily. For example, to alias a bunch of commonly used src/ folders:

webpack.config.js

const path = require('path');

module.exports = {
  //...
  resolve: {
    alias: {
      Utilities: path.resolve(__dirname, 'src/utilities/'),
      Templates: path.resolve(__dirname, 'src/templates/'),
    },
  },
};

Now, instead of using relative paths when importing like so:

import Utility from '../../utilities/utility';

you can use the alias:

import Utility from 'Utilities/utility';

A trailing $ can also be added to the given object's keys to signify an exact match:

webpack.config.js

const path = require('path');

module.exports = {
  //...
  resolve: {
    alias: {
      xyz$: path.resolve(__dirname, 'path/to/file.js'),
    },
  },
};

which would yield these results:

import Test1 from 'xyz'; // Exact match, so path/to/file.js is resolved and imported
import Test2 from 'xyz/file.js'; // Not an exact match, normal resolution takes place

The following table explains other cases:

index.js may resolve to another file if defined in the package.json.

/abc/node_modules may resolve in /node_modules too.

module.exports = {
  //...
  resolve: {
    alias: {
      _: [
        path.resolve(__dirname, 'src/utilities/'),
        path.resolve(__dirname, 'src/templates/'),
      ],
    },
  },
};

Setting resolve.alias to false will tell webpack to ignore a module.

module.exports = {
  //...
  resolve: {
    alias: {
      'ignored-module': false,
      './ignored-module': false,
    },
  },
};

resolve.aliasFields

[string]: ['browser']

Specify a field, such as browser, to be parsed according to this specification.

webpack.config.js

module.exports = {
  //...
  resolve: {
    aliasFields: ['browser'],
  },
};

resolve.cacheWithContext

boolean

If unsafe cache is enabled, includes request.context in the cache key. This option is taken into account by the enhanced-resolve module. context in resolve caching is ignored when resolve or resolveLoader plugins are provided. This addresses a performance regression.

resolve.conditionNames

string[]

Condition names for exports field which defines entry points of a package.

webpack.config.js

module.exports = {
  //...
  resolve: {
    conditionNames: ['require', 'node'],
  },
};

resolve.descriptionFiles

[string] = ['package.json']

The JSON files to use for descriptions.

webpack.config.js

module.exports = {
  //...
  resolve: {
    descriptionFiles: ['package.json'],
  },
};

resolve.enforceExtension

boolean = false

If true, it will not allow extension-less files. So by default require('./foo') works if ./foo has a .js extension, but with this enabled only require('./foo.js') will work.

webpack.config.js

module.exports = {
  //...
  resolve: {
    enforceExtension: false,
  },
};

resolve.extensions

[string] = ['.js', '.json', '.wasm']

Attempt to resolve these extensions in order. If multiple files share the same name but have different extensions, webpack will resolve the one with the extension listed first in the array and skip the rest.

webpack.config.js

module.exports = {
  //...
  resolve: {
    extensions: ['.js', '.json', '.wasm'],
  },
};

which is what enables users to leave off the extension when importing:

import File from '../path/to/file';

Note that using resolve.extensions like above will override the default array, meaning that webpack will no longer try to resolve modules using the default extensions. However you can use '...' to access the default extensions:

module.exports = {
  //...
  resolve: {
    extensions: ['.ts', '...'],
  },
};

resolve.fallback

object

Redirect module requests when normal resolving fails.

webpack.config.js

module.exports = {
  //...
  resolve: {
    fallback: {
      abc: false, // do not include a polyfill for abc
      xyz: path.resolve(__dirname, 'path/to/file.js'), // include a polyfill for xyz
    },
  },
};

Webpack 5 no longer polyfills Node.js core modules automatically which means if you use them in your code running in browsers or alike, you will have to install compatible modules from npm and include them yourself. Here is a list of polyfills webpack has used before webpack 5:

module.exports = {
  //...
  resolve: {
    fallback: {
      assert: require.resolve('assert'),
      buffer: require.resolve('buffer'),
      console: require.resolve('console-browserify'),
      constants: require.resolve('constants-browserify'),
      crypto: require.resolve('crypto-browserify'),
      domain: require.resolve('domain-browser'),
      events: require.resolve('events'),
      http: require.resolve('stream-http'),
      https: require.resolve('https-browserify'),
      os: require.resolve('os-browserify/browser'),
      path: require.resolve('path-browserify'),
      punycode: require.resolve('punycode'),
      process: require.resolve('process/browser'),
      querystring: require.resolve('querystring-es3'),
      stream: require.resolve('stream-browserify'),
      string_decoder: require.resolve('string_decoder'),
      sys: require.resolve('util'),
      timers: require.resolve('timers-browserify'),
      tty: require.resolve('tty-browserify'),
      url: require.resolve('url'),
      util: require.resolve('util'),
      vm: require.resolve('vm-browserify'),
      zlib: require.resolve('browserify-zlib'),
    },
  },
};

resolve.mainFields

[string]

When importing from an npm package, e.g. import * as D3 from 'd3', this option will determine which fields in its package.json are checked. The default values will vary based upon the target specified in your webpack configuration.

When the target property is set to webworker, web, or left unspecified:

webpack.config.js

module.exports = {
  //...
  resolve: {
    mainFields: ['browser', 'module', 'main'],
  },
};

For any other target (including node):

webpack.config.js

module.exports = {
  //...
  resolve: {
    mainFields: ['module', 'main'],
  },
};

For example, consider an arbitrary library called upstream with a package.json that contains the following fields:

{
  "browser": "build/upstream.js",
  "module": "index"
}

When we import * as Upstream from 'upstream' this will actually resolve to the file in the browser property. The browser property takes precedence because it's the first item in mainFields. Meanwhile, a Node.js application bundled by webpack will first try to resolve using the file in the module field.

resolve.mainFiles

[string] = ['index']

The filename to be used while resolving directories.

webpack.config.js

module.exports = {
  //...
  resolve: {
    mainFiles: ['index'],
  },
};

resolve.exportsFields

[string] = ['exports']

Fields in package.json that are used for resolving module requests. See package-exports guideline for more information.

webpack.config.js

module.exports = {
  //...
  resolve: {
    exportsFields: ['exports', 'myCompanyExports'],
  },
};

resolve.modules

[string] = ['node_modules']

Tell webpack what directories should be searched when resolving modules.

Absolute and relative paths can both be used, but be aware that they will behave a bit differently.

A relative path will be scanned similarly to how Node scans for node_modules, by looking through the current directory as well as its ancestors (i.e. ./node_modules, ../node_modules, and on).

With an absolute path, it will only search in the given directory.

webpack.config.js

module.exports = {
  //...
  resolve: {
    modules: ['node_modules'],
  },
};

If you want to add a directory to search in that takes precedence over node_modules/:

webpack.config.js

const path = require('path');

module.exports = {
  //...
  resolve: {
    modules: [path.resolve(__dirname, 'src'), 'node_modules'],
  },
};

resolve.unsafeCache

RegExp [RegExp] boolean: true

Enable aggressive, but unsafe, caching of modules. Passing true will cache everything.

webpack.config.js

module.exports = {
  //...
  resolve: {
    unsafeCache: true,
  },
};

A regular expression, or an array of regular expressions, can be used to test file paths and only cache certain modules. For example, to only cache utilities:

webpack.config.js

module.exports = {
  //...
  resolve: {
    unsafeCache: /src\/utilities/,
  },
};

resolve.useSyncFileSystemCalls

boolean

Use synchronous filesystem calls for the resolver.

webpack.config.js

module.exports = {
  //...
  resolve: {
    useSyncFileSystemCalls: true,
  },
};

resolve.plugins

[Plugin]

A list of additional resolve plugins which should be applied. It allows plugins such as DirectoryNamedWebpackPlugin.

webpack.config.js

module.exports = {
  //...
  resolve: {
    plugins: [new DirectoryNamedWebpackPlugin()],
  },
};

resolve.preferRelative

boolean

When enabled, webpack would prefer to resolve module requests as relative requests instead of using modules from node_modules directories.

webpack.config.js

module.exports = {
  //...
  resolve: {
    preferRelative: true,
  },
};

src/index.js

// let's say `src/logo.svg` exists
import logo1 from 'logo.svg'; // this is viable when `preferRelative` enabled
import logo2 from './logo.svg'; // otherwise you can only use relative path to resolve logo.svg

// `preferRelative` is enabled by default for `new URL()` case
const b = new URL('module/path', import.meta.url);
const a = new URL('./module/path', import.meta.url);

resolve.preferAbsolute

boolean

Prefer absolute paths to resolve.roots when resolving.

webpack.config.js

module.exports = {
  //...
  resolve: {
    preferAbsolute: true,
  },
};

resolve.symlinks

boolean = true

Whether to resolve symlinks to their symlinked location.

When enabled, symlinked resources are resolved to their real path, not their symlinked location. Note that this may cause module resolution to fail when using tools that symlink packages (like npm link).

webpack.config.js

module.exports = {
  //...
  resolve: {
    symlinks: true,
  },
};

resolve.cachePredicate

function(module) => boolean

A function which decides whether a request should be cached or not. An object is passed to the function with path and request properties. It must return a boolean.

webpack.config.js

module.exports = {
  //...
  resolve: {
    cachePredicate: (module) => {
      // additional logic
      return true;
    },
  },
};

resolve.restrictions

[string, RegExp]

A list of resolve restrictions to restrict the paths that a request can be resolved on.

webpack.config.js

module.exports = {
  //...
  resolve: {
    restrictions: [/\.(sass|scss|css)$/],
  },
};

resolve.roots

[string]

A list of directories where requests of server-relative URLs (starting with '/') are resolved, defaults to context configuration option. On non-Windows systems these requests are resolved as an absolute path first.

webpack.config.js

const fixtures = path.resolve(__dirname, 'fixtures');
module.exports = {
  //...
  resolve: {
    roots: [__dirname, fixtures],
  },
};

resolve.importsFields

[string]

Fields from package.json which are used to provide the internal requests of a package (requests starting with # are considered internal).

webpack.config.js

module.exports = {
  //...
  resolve: {
    importsFields: ['browser', 'module', 'main'],
  },
};

resolve.byDependency

Configure resolve options by the type of module request.

• Type: [type: string]: ResolveOptions
• Example:

  module.exports = {
    // ...
    resolve: {
      byDependency: {
        // ...
        esm: {
          mainFields: ['browser', 'module'],
        },
        commonjs: {
          aliasFields: ['browser'],
        },
        url: {
          preferRelative: true,
        },
      },
    },
  };

resolveLoader

object { modules [string] = ['node_modules'], extensions [string] = ['.js', '.json'], mainFields [string] = ['loader', 'main']}

This set of options is identical to the resolve property set above, but is used only to resolve webpack's loader packages.

webpack.config.js

module.exports = {
  //...
  resolveLoader: {
    modules: ['node_modules'],
    extensions: ['.js', '.json'],
    mainFields: ['loader', 'main'],
  },
};

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