#EnvironmentPlugin

EnvironmentPlugin is shorthand for defining selected process.env values with DefinePlugin. It reads environment variables when Rspack builds and replaces the corresponding process.env.* expressions in your bundled code.

#Examples

#Basic usage

Pass environment variable names as separate arguments or as an array. The following calls are equivalent:

new rspack.EnvironmentPlugin('NODE_ENV', 'DEBUG');

new rspack.EnvironmentPlugin(['NODE_ENV', 'DEBUG']);

Both configurations create definitions equivalent to:

new rspack.DefinePlugin({
  'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV),
  'process.env.DEBUG': JSON.stringify(process.env.DEBUG),
});

If a requested variable is missing and has no default value, compilation fails with an EnvVariableNotDefinedError.

#Using default values

Pass an object to provide a default value for each variable. A default is used only when the corresponding key is undefined in process.env when the build starts.

new rspack.EnvironmentPlugin({
  NODE_ENV: 'development',
  DEBUG: false,
});

EnvironmentPlugin serializes default values with JSON.stringify before passing them to DefinePlugin. As a result, JSON-compatible defaults preserve their types: the false default above is injected as a boolean rather than a string.

Use undefined for a variable that must be provided during the build. If it is missing, compilation fails. Use null to provide an optional variable with a null fallback.

For example, suppose entry.js contains:

if (process.env.NODE_ENV === 'production') {
  console.log('Welcome to production');
}
if (process.env.DEBUG) {
  console.log('Debugging output');
}

If NODE_ENV=production is set for the build and DEBUG is unset, the replacements are equivalent to:

if ('production' === 'production') {
  // process.env.NODE_ENV comes from the environment
  console.log('Welcome to production');
}
if (false) {
  // process.env.DEBUG uses the default value
  console.log('Debugging output');
}

If DEBUG=false is set and NODE_ENV is unset, the replacements are equivalent to:

if ('development' === 'production') {
  // process.env.NODE_ENV uses the default value
  console.log('Welcome to production');
}
if ('false') {
  // process.env.DEBUG comes from the environment
  console.log('Debugging output');
}

#Using Git metadata

Default values can also be computed while loading the Rspack configuration. This example exposes the version and author date of the current Git commit:

import { execFileSync } from 'node:child_process';

function git(...args) {
  return execFileSync('git', args, { encoding: 'utf8' }).trim();
}

new rspack.EnvironmentPlugin({
  GIT_VERSION: git('describe', '--always'),
  GIT_AUTHOR_DATE: git('log', '-1', '--format=%aI'),
});

#Loading .env files

EnvironmentPlugin does not read .env files by itself. To load variables from a file, use a third-party plugin such as dotenv-webpack:

PUBLIC_API_ORIGIN=https://api.example.com
FEATURE_ENABLED=true

import Dotenv from 'dotenv-webpack';

new Dotenv({
  path: './.env',
});

Only load values that are safe to embed in client-side code, because injected values can be read from the generated bundle.

#Options

• Type:

declare class EnvironmentPlugin {
  constructor(...keys: string[]);
  constructor(keys: string[]);
  constructor(defaultValues: Record<string, any>);
}

Use either string form when every selected variable is required. Use the object form to provide default values; assigning undefined still marks that variable as required.

This page is adapted from webpack documentation under the CC BY 4.0, with modifications.