dotenv — Node.js Environment Variable Loader

dotenv is a zero-dependency module that loads environment variables from a .env file into process.env.

Use Cases

Use when users need to load .env files, configure environment variables, handle API keys and sensitive configuration, set up multi-environment variables, or use dotenv/dotenvx. Trigger words include "dotenv," "environment variables," "env file," "dotenvx," "process.env," "encrypted env," etc.

Installation

npm install dotenv
# or
bun add dotenv
yarn add dotenv
pnpm add dotenv

Basic Usage

Create a .env file

# .env
HELLO="World"
OPENAI_API_KEY="sk-your-key-here"
DATABASE_URL="postgres://localhost/mydb"
PORT=3000
DEBUG=true

Load into your application

// CommonJS — call at the top of your entry file as early as possible
require('dotenv').config()

console.log(process.env.HELLO)       // "World"
console.log(process.env.OPENAI_API_KEY)

// ES Module
import 'dotenv/config'

// Or when custom configuration is needed:
import dotenv from 'dotenv'
dotenv.config({ path: '/custom/path/to/.env' })

$ node index.js
◇ injected env (4) from .env

.gitignore Security

Never commit .env to version control:

# .gitignore
.env
.env.local
.env.*.local

Commit a .env.example template file (without real keys) for team members' reference.

config() Options

dotenv.config({
  path: '/custom/path/to/.env',     // Default: path.resolve(process.cwd(), '.env')
  encoding: 'utf8',                  // File encoding, default utf8
  debug: true,                       // Enable debug logging
  override: false,                   // Whether to override existing process.env values
  processEnv: {},                    // Custom target object (default process.env)
  quiet: false,                      // v17.2+ quiet mode
})

Return value:

const result = dotenv.config()
// result.parsed → { HELLO: 'World', PORT: '3000' }
// result.error  → Error or undefined

Environment Variable Configuration (DOTENV_CONFIG_*)

Config options can be overridden via environment variables (CLI arguments take higher priority):

DOTENV_CONFIG_PATH=/custom/path/.env \
DOTENV_CONFIG_DEBUG=true \
DOTENV_CONFIG_QUIET=true \
node index.js

Or within the .env file itself:

DOTENV_CONFIG_QUIET=true
HELLO="World"

parse() — Manual Parsing

const dotenv = require('dotenv')

const buf = Buffer.from('HELLO=world\nPORT=3000')
const config = dotenv.parse(buf)
// { HELLO: 'world', PORT: '3000' }

Preload

Load without requiring dotenv in your code by preloading via the command line:

node -r dotenv/config your_script.js
node -r dotenv/config your_script.js dotenv_config_path=/custom/path/.env

.env File Format Details

Basic Format

KEY=value
KEY2="value with spaces"
KEY3='single quoted value'

Comments

# This is a comment
SECRET_KEY=abc123  # End-of-line comment
HASH="value-with-#-in-it"  # Values containing # must be wrapped in quotes

Multiline Values (v15.0.0+)

PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----
Line1
Line2
-----END RSA PRIVATE KEY-----"

# Or use \n
PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----\nLine1\nLine2\n-----END RSA PRIVATE KEY-----"

TypeScript

import dotenv from 'dotenv'
dotenv.config()

// Or
import 'dotenv/config'

// Declare type augmentation
declare global {
  namespace NodeJS {
    interface ProcessEnv {
      OPENAI_API_KEY: string
      DATABASE_URL: string
    }
  }
}

dotenvx — Advanced Features

dotenvx is an upgraded CLI tool for dotenv that provides advanced features such as encryption, variable expansion, and multi-environment management.

Installation

npm install -g @dotenvx/dotenvx
# or
brew install dotenvx
# or
curl -fsS https://dotenvx.sh/ | sh

Variable Expansion

# .env
USERNAME="admin"
DATABASE_URL="postgres://${USERNAME}@localhost/mydb"

dotenvx run -- node index.js

Command Substitution

DATABASE_URL="postgres://$(whoami)@localhost/mydb"

Multi-Environment Management

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

# Load a specific environment
dotenvx run -f=.env.production -- node index.js

# Load multiple files (leftmost takes higher priority)
dotenvx run -f=.env.local -f=.env -- node index.js

Encryption (Safe to Commit to Git)

# Encrypt the .env file
dotenvx encrypt -f .env.production

# Generate .env.keys (contains the decryption key) → add to .gitignore
# The encrypted .env.production can now be safely committed

# Set the decryption key during deployment
heroku config:set DOTENV_PRIVATE_KEY_PRODUCTION="<key from .env.keys>"

# Automatic decryption at runtime
dotenvx run -- node index.js

Use Case Comparison

Common Patterns and Best Practices

Application Entry Loading

// app.js — First line
require('dotenv').config()

const express = require('express')
const app = express()
// All subsequent modules can read values via process.env

Loading with Validation

const dotenv = require('dotenv')
dotenv.config()

const required = ['DATABASE_URL', 'SECRET_KEY']
for (const key of required) {
  if (!process.env[key]) {
    throw new Error(`Missing required env var: ${key}`)
  }
}

Monorepo Scenario

apps/backend/
├── .env          ← Place in the app's runtime directory
├── app.js
└── package.json

Multi-Environment File Recommendations

• .env — Local development (default)
• .env.production — Production environment
• .env.test — Testing environment
• .env.example — Template (commit to git, without real values)

Do not let .env.production inherit values from .env — each environment file should be independently complete.

Logging Control

# Suppress injection logs
DOTENV_CONFIG_QUIET=true node index.js

Troubleshooting