Command Line Interface

For proper usage and easy distribution of this configuration, webpack can be configured with webpack.config.js. Any parameters sent to the CLI will map to a corresponding parameter in the configuration file.

Read the installation guide if you don't already have webpack and CLI installed.

Commands

webpack-cli offers a variety of commands to make working with webpack easy. By default webpack ships with

Command	Usage	Description
build	build|bundle|b [entries...] [options]	Run webpack (default command, can be omitted).
configtest	configtest|t [config-path]	Validate a webpack configuration.
help	help|h [command] [option]	Display help for commands and options.
info	info|i [options]	Outputs information about your system.
init	init|c [scaffold...] [options]	Initialize a new webpack configuration.
loader	loader|l [output-path]	Scaffold a loader.
plugin	plugin|p [output-path]	Scaffold a plugin.
serve	serve|s [options]	Run the webpack-dev-server.
version	version|v [commands...]	Output the version number of webpack, webpack-cli and webpack-dev-server.
watch	watch|w [entries...] [options]	Run webpack and watch for files changes.

Flags

By default webpack ships with the following flags:

Flag / Alias	Type	Description
--entry	string[]	The entry point(s) of your application e.g. ./src/main.js
--config, -c	string[]	Provide path to a webpack configuration file e.g. ./webpack.config.js
--config-name	string[]	Name of the configuration to use
--name	string	Name of the configuration. Used when loading multiple configurations
--color	boolean	Enable colors on console
--merge, -m	boolean	Merge two or more configurations using webpack-merge e.g. -c ./webpack.config.js -c ./webpack.test.config.js
--env	string[]	Environment passed to the configuration when it is a function
--node-env	string	Set process.env.NODE_ENV to the specified value
--progress	boolean, string	Print compilation progress during build
--help	boolean	Outputs list of supported flags and commands
--output-path, -o	string	Output location of the file generated by webpack e.g. ./dist
--target, -t	string[]	Sets the build target
--watch, -w	boolean	Watch for file changes
--watch-options-stdin	boolean	Stop watching when stdin stream has ended
--hot, -h	boolean	Enables Hot Module Replacement
--devtool, -d	string	Controls if and how source maps are generated.
--prefetch	string	Prefetch this request
--json, -j	boolean, string	Prints result as JSON or store it in a file
--mode	string	Defines the mode to pass to webpack
--version, -v	boolean	Get current version
--stats	boolean, string	It instructs webpack on how to treat the stats
--analyze	boolean	It invokes webpack-bundle-analyzer plugin to get bundle information

Negated Flags

Flag	Description
--no-color	Disables any color on the console
--no-hot	Disables hot reloading if you have it enabled via your config
--no-stats	Disables any compilation stats emitted by webpack
--no-watch	Do not watch for file changes
--no-devtool	Do not generate source maps
--no-watch-options-stdin	Do not stop watching when stdin stream has ended

Core Flags

Starting CLI v4 and webpack v5, CLI imports the entire configuration schema from webpack core to allow tuning almost every configuration option from the command line.

Here's the list of all the core flags supported by webpack v5 with CLI v4 - link

For example if you want to enable performance hints in your project you'd use this option in configuration, with core flags you can do -

npx webpack --performance-hints warning

Usage

With configuration file

npx webpack [--config webpack.config.js]

See configuration for the options in the configuration file.

Without configuration file

npx webpack --entry <entry> -o <output-path>

example

npx webpack --entry ./first.js --entry ./second.js --output-path /build

<entry>

A filename or a set of named filenames which act as the entry point to build your project. You can pass multiple entries (every entry is loaded on startup). Following are the multiple ways of specifying entry file(s) via CLI -

npx webpack ./first-entry.js

npx webpack --entry ./first-entry.js

npx webpack ./first-entry.js ./other-entry.js

npx webpack --entry ./first-entry.js ./other-entry.js

<output>

A path for the bundled file to be saved in. It will be mapped to the configuration options output.path.

Example

If your project structure is as follows -

.
├── dist
├── index.html
└── src
    ├── index.js
    ├── index2.js
    └── others.js

npx webpack ./src/index.js -o dist

This will bundle your source code with entry as index.js, and the output bundle file will have a path of dist.

asset main.js 142 bytes [compared for emit] [minimized] (name: main)
./src/index.js 30 bytes [built] [code generated]
./src/others.js 1 bytes [built] [code generated]
webpack 5.1.0 compiled successfully in 187 ms

npx webpack ./src/index.js ./src/others2.js -o dist/

This will form the bundle with both the files as separate entry points.

asset main.js 142 bytes [compared for emit] [minimized] (name: main)
./src/index.js 30 bytes [built] [code generated]
./src/others2.js 1 bytes [built] [code generated]
./src/others.js 1 bytes [built] [code generated]
webpack 5.1.0 compiled successfully in 198 ms

Default Configurations

CLI will look for some default configurations in the path of your project, here are the config files picked up by CLI.

This is the lookup priority in increasing order

example - config file lookup will be in order of .webpack/webpackfile > .webpack/webpack.config.js > webpack.config.js

'webpack.config',
'.webpack/webpack.config',
'.webpack/webpackfile',

Common Options

help

List basic commands and flags available on the cli

Both webpack help [command] [option] and webpack [command] --help are valid to get help:

npx webpack --help

# or

npx webpack help

List all supported commands and flags by cli

npx webpack --help=verbose

See help for a specific command or option

npx webpack help --mode

version

Show version of installed packages and sub-packages

To inspect the version of webpack and webpack-cli you are using just run command:

npx webpack --version

# or

npx webpack version

This will output the following result:

webpack 5.11.1
webpack-cli 4.3.1

It will output the version of webpack-dev-server as well if you have it installed:

webpack 5.11.1
webpack-cli 4.3.1
webpack-dev-server 3.11.1

To inspect the version of any webpack-cli sub-package (like @webpack-cli/init) just run command similar to the following:

npx webpack init --version

This will output the following result:

@webpack-cli/init 1.0.3
webpack-cli 4.2.0
webpack 5.4.0

config

Build source using a configuration file

Specify a different configuration file other than webpack.config.js, which is one of the defaults.

npx webpack --config example.config.js

config-name

In case your configuration file exports multiple configurations, you can use --config-name to specify which configuration to run.

Consider the following webpack.config.js:

module.exports = [
  {
    output: {
      filename: './dist-first.js',
    },
    name: 'first',
    entry: './src/first.js',
    mode: 'development',
  },
  {
    output: {
      filename: './dist-second.js',
    },
    name: 'second',
    entry: './src/second.js',
    mode: 'development',
  },
  {
    output: {
      filename: './dist-third.js',
    },
    name: 'third',
    entry: './src/third.js',
    mode: 'none',
    stats: 'verbose',
  },
];

To run only the second configuration:

npx webpack --config-name second

You can also pass multiple values:

npx webpack --config-name first --config-name second

merge

You can merge two or more different webpack configurations with the help of --merge:

npx webpack --config ./first.js --config ./second.js --merge

json

Print result of webpack as JSON

npx webpack --json

If you want to store stats as json instead of printing it, you can use -

npx webpack --json stats.json

In every other case, webpack prints out a set of stats showing bundle, chunk and timing details. Using this option, the output can be a JSON object. This response is accepted by webpack's analyse tool, or chrisbateman's webpack-visualizer, or th0r's webpack-bundle-analyzer. The analyse tool will take in the JSON and provide all the details of the build in graphical form.

Environment Options

When the webpack configuration exports a function, an "environment" may be passed to it.

npx webpack --env production    # env.production = true

The --env argument accepts multiple values:

Invocation	Resulting environment
npx webpack --env prod	{ prod: true }
npx webpack --env prod --env min	{ prod: true, min: true }
npx webpack --env platform=app --env production	{ platform: "app", production: true }
npx webpack --env app.platform="staging" --env app.name="test"	{ app: { platform: "staging", name: "test" }

NODE_ENV

You can use --node-env option to set process.env.NODE_ENV:

npx webpack --node-env production   # process.env.NODE_ENV = 'production'

Configuration Options

Parameter	Explanation	Input type	Default
--config	Path to the configuration file	string[]	Default Configs
--config-name	Name of the configuration to use	string[]	-
--env	Environment passed to the configuration, when it is a function	string[]	-

Analyzing Bundle

You can also use webpack-bundle-analyzer to analyze your output bundles emitted by webpack. You can use --analyze flag to invoke it via CLI.

npx webpack --analyze

Progress

To check the progress of any webpack compilation you can use the --progress flag.

npx webpack --progress

To collect profile data for progress steps you can pass profile as value to --progress flag.

npx webpack --progress=profile

Pass CLI arguments to Node.js

To pass arguments directly to Node.js process, you can use the NODE_OPTIONS option.

For example, to increase the memory limit of Node.js process to 4 GB

NODE_OPTIONS="--max-old-space-size=4096" webpack

Also, you can pass multiple options to Node.js process

NODE_OPTIONS="--max-old-space-size=4096 -r /path/to/preload/file.js" webpack

Exit codes and their meanings

Exit Code	Description
0	Success
1	Errors from webpack
2	Configuration/options problem or an internal error

Environment Variables

Environment Variable	Description
WEBPACK_SERVE	true if serve|s is being used.
WEBPACK_BUILD	true if build|bundle|b is being used.
WEBPACK_WATCH	true if --watch|watch|w is being used.

You can use the above environment variables inside your webpack configuration:

module.exports = (env, argv) => {
  return {
    mode: env.WEBPACK_SERVE ? 'development' : 'production',
  };
};