Mode

Providing the mode configuration option tells webpack to use its built-in optimizations accordingly.

string = 'production': 'none' | 'development' | 'production'

Usage

Provide the mode option in the config:

module.exports = {
  mode: 'development',
};

or pass it as a CLI argument:

webpack --mode=development

The following string values are supported:

Option	Description
development	Sets process.env.NODE_ENV on DefinePlugin to value development. Enables useful names for modules and chunks.
production	Sets process.env.NODE_ENV on DefinePlugin to value production. Enables deterministic mangled names for modules and chunks, FlagDependencyUsagePlugin, FlagIncludedChunksPlugin, ModuleConcatenationPlugin, NoEmitOnErrorsPlugin and TerserPlugin.
none	Opts out of any default optimization options

If not set, webpack sets production as the default value for mode.

Mode: development

// webpack.development.config.js
module.exports = {
  mode: 'development',
};

Mode: production

// webpack.production.config.js
module.exports = {
  mode: 'production',
};

Mode: none

// webpack.custom.config.js
module.exports = {
  mode: 'none',
};

If you want to change the behavior according to the mode variable inside the webpack.config.js, you have to export a function instead of an object:

var config = {
  entry: './app.js',
  //...
};

module.exports = (env, argv) => {
  if (argv.mode === 'development') {
    config.devtool = 'source-map';
  }

  if (argv.mode === 'production') {
    //...
  }

  return config;
};