dotenv

What is dotenv?

The dotenv npm package is used to load environment variables from a .env file into process.env, providing a convenient way to configure your application's environment during development. It helps in managing sensitive credentials and configuration options by keeping them out of the codebase.

What are dotenv's main functionalities?

Basic Configuration

This is the simplest use case for dotenv. By calling `require('dotenv').config();`, dotenv reads the .env file, parses the contents, and loads them into `process.env`. After this, environment variables can be accessed using `process.env.VAR_NAME`.

require('dotenv').config();

Custom Path

If your .env file is not located in the root directory or you have multiple .env files, you can specify a custom path to your .env file using the `path` option.

require('dotenv').config({ path: '/custom/path/to/.env' });

Debugging

To assist in debugging, you can enable debug output by setting the `debug` option to `true`. This will log any errors to the console while reading the .env file.

require('dotenv').config({ debug: process.env.DEBUG });

Other packages similar to dotenv

dotenv-expand

dotenv-expand is an extension for dotenv. It allows you to have environment variables in your .env file that reference other environment variables, similar to variable expansion in Unix shell scripts. It's useful when you need to reduce redundancy in your .env files.

cross-env

cross-env allows you to set and use environment variables across platforms without worrying about platform-specific differences in how environment variables are set. Unlike dotenv, which is focused on loading variables from a file, cross-env is more about providing scripts with environment variables in a cross-platform way.

env-cmd

env-cmd is another npm package that allows you to specify a file containing environment variable definitions and then run a given command using those variables. It's similar to dotenv but is more focused on injecting environment variables into the command line for scripts, rather than loading them into `process.env`.

README

dotenv

Dotenv is a zero-dependency module that loads environment variables from a .env file into process.env. Storing configuration in the environment separate from code is based on The Twelve-Factor App methodology.

Install

# with npm
npm install dotenv

# or with Yarn
yarn add dotenv

Usage

As early as possible in your application, require and configure dotenv.

require('dotenv').config()

Create a .env file in the root directory of your project. Add environment-specific variables on new lines in the form of NAME=VALUE. For example:

DB_HOST=localhost
DB_USER=root
DB_PASS=s1mpl3

process.env now has the keys and values you defined in your .env file.

const db = require('db')
db.connect({
  host: process.env.DB_HOST,
  username: process.env.DB_USER,
  password: process.env.DB_PASS
})

Preload

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. This is the preferred approach when using import instead of require.

$ 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/your/env/vars

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

Config

config will read your .env file, parse the contents, assign it to process.env, and return an Object with a parsed key containing the loaded content or an error key if it failed.

const result = dotenv.config()

if (result.error) {
  throw result.error
}

console.log(result.parsed)

You can additionally, pass options to config.

Options

Path

Default: path.resolve(process.cwd(), '.env')

You may specify a custom path if your file containing environment variables is located elsewhere.

require('dotenv').config({ path: '/full/custom/path/to/your/env/vars' })

Encoding

Default: utf8

You may specify the encoding of your file containing environment variables.

require('dotenv').config({ encoding: 'latin1' })

Debug

Default: false

You may turn on logging to help debug why certain keys or values are not being set as you expect.

require('dotenv').config({ debug: process.env.DEBUG })

Parse

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' }

Options

Debug

Default: false

You may turn on logging to help debug why certain keys or values are not being set as you expect.

const dotenv = require('dotenv')
const buf = Buffer.from('hello world')
const opt = { debug: true }
const config = dotenv.parse(buf, opt)
// expect a debug message because the buffer is not in KEY=VAL form

Rules

The parsing engine currently supports the following rules:

• BASIC=basic becomes {BASIC: 'basic'}
• empty lines are skipped
• lines beginning with # are treated as comments
• 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'}

FAQ

Should I commit my .env file?

No. We strongly recommend against committing your .env file to version control. It should only include environment-specific values such as database passwords or API keys. Your production database should have a different password than your development database.

Should I have multiple .env files?

No. We strongly recommend against having a "main" .env file and an "environment" .env file like .env.test. Your config should vary between deploys, and you should not be sharing values between environments.

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

What happens to environment variables that were already set?

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. This behavior allows you to override all .env configurations with a machine-specific environment, although it is not recommended.

If you want to override process.env you can do something like this:

const fs = require('fs')
const dotenv = require('dotenv')
const envConfig = dotenv.parse(fs.readFileSync('.env.override'))
for (const k in envConfig) {
  process.env[k] = envConfig[k]
}

Can I customize/write plugins for dotenv?

For dotenv@2.x.x: Yes. dotenv.config() now 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)

What about variable expansion?

Try dotenv-expand

How do I use dotenv with import?

ES2015 and beyond offers modules that allow you to export any top-level function, class, var, let, or const.

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

You must run dotenv.config() before referencing any environment variables. Here's an example of problematic code:

errorReporter.js:

import { Client } from 'best-error-reporting-service'

export const client = new Client(process.env.BEST_API_KEY)

index.js:

import dotenv from 'dotenv'
import errorReporter from './errorReporter'

dotenv.config()
errorReporter.client.report(new Error('faq example'))

client will not be configured correctly because it was constructed before dotenv.config() was executed. There are (at least) 3 ways to make this work.

1. Preload dotenv: node --require dotenv/config index.js (Note: you do not need to import dotenv with this approach)
2. Import dotenv/config instead of dotenv (Note: you do not need to call dotenv.config() and must pass options via the command line or environment variables with this approach)
3. Create a separate file that will execute config first as outlined in this comment on #133

Contributing Guide

See CONTRIBUTING.md

Change Log

See CHANGELOG.md

Who's using dotenv?

These npm modules depend on it.

Projects that expand it often use the keyword "dotenv" on npm.