Mode

              string

module.exports = {
  mode: 'production'
};
webpack --mode=production

The following string values are supported:

Option

Description

​​development​​

Sets ​​process.env.NODE_ENV​​​ on ​​DefinePlugin​​​ to value ​​development​​​. Enables ​​NamedChunksPlugin​​​ and ​​NamedModulesPlugin​​.

​​production​​

Sets ​​process.env.NODE_ENV​​​ on ​​DefinePlugin​​​ to value ​​production​​​. Enables ​​FlagDependencyUsagePlugin​​​, ​​FlagIncludedChunksPlugin​​​, ​​ModuleConcatenationPlugin​​​, ​​NoEmitOnErrorsPlugin​​​, ​​OccurrenceOrderPlugin​​​, ​​SideEffectsFlagPlugin​​​ and ​​UglifyJsPlugin​​.

​​none​​

Opts out of any default optimization options

If not set, webpack sets ​​production​​​ as the default value for ​​mode​​. The supported values for mode are:

Please remember that setting ​​NODE_ENV​​​ doesn't automatically set ​​mode​​.

// webpack.development.config.js
module.exports = {
+ mode: 'development'
- devtool: 'eval',
- plugins: [
-   new webpack.NamedModulesPlugin(),
-   new webpack.NamedChunksPlugin(),
-   new webpack.DefinePlugin({ "process.env.NODE_ENV": JSON.stringify("development") }),
- ]
}

Mode: production 

// webpack.production.config.js
module.exports = {
+  mode: 'production',
-  plugins: [
-    new UglifyJsPlugin(/* ... */),
-    new webpack.DefinePlugin({ "process.env.NODE_ENV": JSON.stringify("production") }),
-    new webpack.optimize.ModuleConcatenationPlugin(),
-    new webpack.NoEmitOnErrorsPlugin()
-  ]
}

Mode: none 

// webpack.custom.config.js
module.exports = {
+  mode: 'none',
-  plugins: [
-  ]
}

f 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;
};