Import with ES6:

import 'dotenv/config'

ES6 import if you need to set config options:

import dotenv from 'dotenv'
dotenv.config({ path: '/custom/path/to/.env' })

bun add dotenv

yarn add dotenv

pnpm add dotenv

For monorepos with a structure like apps/backend/app.js, put it the .env file in the root of the folder where your app.js process runs.

# app/backend/.env
S3_BUCKET="YOURS3BUCKET"
SECRET_KEY="YOURSECRETKEYGOESHERE"

If you need multiline variables, for example private keys, those are now supported (>= v15.0.0) with line breaks:

PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----
...
Kh9NV...
...
-----END RSA PRIVATE KEY-----"

Alternatively, you can double quote strings and use the \n character:

PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----\nKh9NV...\n-----END RSA PRIVATE KEY-----\n"

Comments may be added to your file on their own line or inline:

# This is a comment
SECRET_KEY=YOURSECRETKEYGOESHERE # comment
SECRET_HASH="something-with-a-#-hash"

Comments begin where a # exists, so if your value contains a # please wrap it in quotes. This is a breaking change from >= v15.0.0 and on.

The engine which parses the contents of your file containing environment variables is available to use. It accepts a String or Buffer and will return an Object with the parsed keys and values.

const dotenv = require('dotenv')
const buf = Buffer.from('BASIC=basic')
const config = dotenv.parse(buf) // will return an object
console.log(typeof config, config) // object { BASIC : 'basic' }

Note: Consider using dotenvx instead of preloading. I am now doing (and recommending) so.

It serves the same purpose (you do not need to require and load dotenv), adds better debugging, and works with ANY language, framework, or platform. – motdotla

You can use the --require (-r) command line option to preload dotenv. By doing this, you do not need to require and load dotenv in your application code.

$ node -r dotenv/config your_script.js

The configuration options below are supported as command line arguments in the format dotenv_config_<option>=value

$ node -r dotenv/config your_script.js dotenv_config_path=/custom/path/to/.env dotenv_config_debug=true

Additionally, you can use environment variables to set configuration options. Command line arguments will precede these.

$ DOTENV_CONFIG_<OPTION>=value node -r dotenv/config your_script.js

$ DOTENV_CONFIG_ENCODING=latin1 DOTENV_CONFIG_DEBUG=true node -r dotenv/config your_script.js dotenv_config_path=/custom/path/to/.env

Use dotenvx for variable expansion.

Reference and expand variables already on your machine for use in your .env file.

# .env
USERNAME="username"
DATABASE_URL="postgres://${USERNAME}@localhost/my_database"

// index.js
console.log('DATABASE_URL', process.env.DATABASE_URL)

$ dotenvx run --debug -- node index.js
[dotenvx@0.14.1] injecting env (2) from .env
DATABASE_URL postgres://username@localhost/my_database

Use dotenvx for command substitution.

Add the output of a command to one of your variables in your .env file.

# .env
DATABASE_URL="postgres://$(whoami)@localhost/my_database"

// index.js
console.log('DATABASE_URL', process.env.DATABASE_URL)

$ dotenvx run --debug -- node index.js
[dotenvx@0.14.1] injecting env (1) from .env
DATABASE_URL postgres://yourusername@localhost/my_database

Use dotenvx for encryption.

Add encryption to your .env files with a single command.

$ dotenvx set HELLO Production -f .env.production
$ echo "console.log('Hello ' + process.env.HELLO)" > index.js

$ DOTENV_PRIVATE_KEY_PRODUCTION="<.env.production private key>" dotenvx run -- node index.js
[dotenvx] injecting env (2) from .env.production
Hello Production

learn more

Use dotenvx to manage multiple environments.

Run any environment locally. Create a .env.ENVIRONMENT file and use -f to load it. It's straightforward, yet flexible.

$ echo "HELLO=production" > .env.production
$ echo "console.log('Hello ' + process.env.HELLO)" > index.js

$ dotenvx run -f=.env.production -- node index.js
Hello production
> ^^

or with multiple .env files

$ echo "HELLO=local" > .env.local
$ echo "HELLO=World" > .env
$ echo "console.log('Hello ' + process.env.HELLO)" > index.js

$ dotenvx run -f=.env.local -f=.env -- node index.js
Hello local

more environment examples

Use dotenvx for production deploys.

Create a .env.production file.

$ echo "HELLO=production" > .env.production

Encrypt it.

$ dotenvx encrypt -f .env.production

Set DOTENV_PRIVATE_KEY_PRODUCTION (found in .env.keys) on your server.

$ heroku config:set DOTENV_PRIVATE_KEY_PRODUCTION=value

Commit your .env.production file to code and deploy.

$ git add .env.production
$ git commit -m "encrypted .env.production"
$ git push heroku main

Dotenvx will decrypt and inject the secrets at runtime using dotenvx run -- node index.js.

Use dotenvx to sync your .env files.

Encrypt them with dotenvx encrypt -f .env and safely include them in source control. Your secrets are securely synced with your git.

This still subscribes to the twelve-factor app rules by generating a decryption key separate from code.

See examples of using dotenv with various frameworks, languages, and configurations.

• nodejs
• nodejs (debug on)
• nodejs (override on)
• nodejs (processEnv override)
• esm
• esm (preload)
• typescript
• typescript parse
• typescript config
• webpack
• webpack (plugin)
• react
• react (typescript)
• express
• nestjs
• fastify

No.

Unless you encrypt it with dotenvx. Then we recommend you do.

Use dotenvx.

We recommend creating one .env file per environment. Use .env for local/development, .env.production for production and so on. This still follows the twelve factor principles as each is attributed individually to its own environment. Avoid custom set ups that work in inheritance somehow (.env.production inherits values form .env for example). It is better to duplicate values if necessary across each .env.environment file.

In a twelve-factor app, env vars are granular controls, each fully orthogonal to other env vars. They are never grouped together as “environments”, but instead are independently managed for each deploy. This is a model that scales up smoothly as the app naturally expands into more deploys over its lifetime.

– The Twelve-Factor App

Additionally, we recommend using dotenvx to encrypt and manage these.

Simply..

// index.mjs (ESM)
import 'dotenv/config' // see https://github.com/motdotla/dotenv#how-do-i-use-dotenv-with-import
import express from 'express'

A little background..

When you run a module containing an import declaration, the modules it imports are loaded first, then each module body is executed in a depth-first traversal of the dependency graph, avoiding cycles by skipping anything already executed.

– ES6 In Depth: Modules

What does this mean in plain language? It means you would think the following would work but it won't.

errorReporter.mjs:

class Client {
  constructor (apiKey) {
    console.log('apiKey', apiKey)

    this.apiKey = apiKey
  }
}

export default new Client(process.env.API_KEY)

index.mjs:

// Note: this is INCORRECT and will not work
import * as dotenv from 'dotenv'
dotenv.config()

import errorReporter from './errorReporter.mjs' // process.env.API_KEY will be blank!

process.env.API_KEY will be blank.

Instead, index.mjs should be written as..

import 'dotenv/config'

import errorReporter from './errorReporter.mjs'

Does that make sense? It's a bit unintuitive, but it is how importing of ES6 modules work. Here is a working example of this pitfall.

There are two alternatives to this approach:

1. Preload with dotenvx: dotenvx run -- node index.js (Note: you do not need to import dotenv with this approach)
2. Create a separate file that will execute config first as outlined in this comment on #133

Yes! dotenv.config() returns an object representing the parsed .env file. This gives you everything you need to continue setting values on process.env. For example:

const dotenv = require('dotenv')
const variableExpansion = require('dotenv-expand')
const myEnv = dotenv.config()
variableExpansion(myEnv)

The parsing engine currently supports the following rules:

• BASIC=basic becomes {BASIC: 'basic'}
• empty lines are skipped
• lines beginning with # are treated as comments
• # marks the beginning of a comment (unless when the value is wrapped in quotes)
• empty values become empty strings (EMPTY= becomes {EMPTY: ''})
• inner quotes are maintained (think JSON) (JSON={"foo": "bar"} becomes {JSON:"{\"foo\": \"bar\"}")
• whitespace is removed from both ends of unquoted values (see more on trim) (FOO= some value becomes {FOO: 'some value'})
• single and double quoted values are escaped (SINGLE_QUOTE='quoted' becomes {SINGLE_QUOTE: "quoted"})
• single and double quoted values maintain whitespace from both ends (FOO=" some value " becomes {FOO: ' some value '})
• double quoted values expand new lines (MULTILINE="new\nline" becomes

{MULTILINE: 'new
line'}

• backticks are supported (BACKTICK_KEY=`This has 'single' and "double" quotes inside of it.`)

Use dotenvx to unlock syncing encrypted .env files over git.

Remove it, remove git history and then install the git pre-commit hook to prevent this from ever happening again.

npm i -g @dotenvx/dotenvx
dotenvx precommit --install

By default, we will never modify any environment variables that have already been set. In particular, if there is a variable in your .env file which collides with one that already exists in your environment, then that variable will be skipped.

If instead, you want to override process.env use the override option.

require('dotenv').config({ override: true })

Use the docker prebuild hook.

# Dockerfile
...
RUN curl -fsS https://dotenvx.sh/ | sh
...
RUN dotenvx prebuild
CMD ["dotenvx", "run", "--", "node", "index.js"]

Your React code is run in Webpack, where the fs module or even the process global itself are not accessible out-of-the-box. process.env can only be injected through Webpack configuration.

If you are using react-scripts, which is distributed through create-react-app, it has dotenv built in but with a quirk. Preface your environment variables with REACT_APP_. See this stack overflow for more details.

If you are using other frameworks (e.g. Next.js, Gatsby...), you need to consult their documentation for how to inject environment variables into the client.

Most likely your .env file is not in the correct place. See this stack overflow.

Turn on debug mode and try again..

require('dotenv').config({ debug: true })

You will receive a helpful error outputted to your console.

You are using dotenv on the front-end and have not included a polyfill. Webpack < 5 used to include these for you. Do the following:

npm install node-polyfill-webpack-plugin

Configure your webpack.config.js to something like the following.

require('dotenv').config()

const path = require('path');
const webpack = require('webpack')

const NodePolyfillPlugin = require('node-polyfill-webpack-plugin')

module.exports = {
  mode: 'development',
  entry: './src/index.ts',
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist'),
  },
  plugins: [
    new NodePolyfillPlugin(),
    new webpack.DefinePlugin({
      'process.env': {
        HELLO: JSON.stringify(process.env.HELLO)
      }
    }),
  ]
};

Alternatively, just use dotenv-webpack which does this and more behind the scenes for you.