{/* The content of this doc is shared between the app and pages router. You can use the <PagesOnly>Content</PagesOnly> component to add content that is specific to the Pages Router. Any shared content should not be wrapped in a component. */}

Next.js comes with built-in support for environment variables, which allows you to do the following:

• Use .env to load environment variables
• Bundle environment variables for the browser by prefixing with NEXT_PUBLIC_

Warning: The default create-next-app template ensures all .env files are added to your .gitignore. You almost never want to commit these files to your repository.

Loading Environment Variables

Next.js has built-in support for loading environment variables from .env* files into process.env.

DB_HOST=localhost
DB_USER=myuser
DB_PASS=mypassword

This loads process.env.DB_HOST, process.env.DB_USER, and process.env.DB_PASS into the Node.js environment automatically allowing you to use them in Next.js data fetching methods and API routes.

For example, using getStaticProps:

export async function getStaticProps() {
  const db = await myDB.connect({
    host: process.env.DB_HOST,
    username: process.env.DB_USER,
    password: process.env.DB_PASS,
  })
  // ...
}

Note: Next.js also supports multiline variables inside of your .env* files:

# .env

# you can write with line breaks
PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----
...
Kh9NV...
...
-----END DSA PRIVATE KEY-----"

# or with `\n` inside double quotes
PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----\nKh9NV...\n-----END DSA PRIVATE KEY-----\n"

Note: If you are using a /src folder, please note that Next.js will load the .env files only from the parent folder and not from the /src folder. This loads process.env.DB_HOST, process.env.DB_USER, and process.env.DB_PASS into the Node.js environment automatically allowing you to use them in Route Handlers.

For example:

export async function GET() {
  const db = await myDB.connect({
    host: process.env.DB_HOST,
    username: process.env.DB_USER,
    password: process.env.DB_PASS,
  })
  // ...
}

Loading Environment Variables with @next/env

If you need to load environment variables outside of the Next.js runtime, such as in a root config file for an ORM or test runner, you can use the @next/env package.

This package is used internally by Next.js to load environment variables from .env* files.

To use it, install the package and use the loadEnvConfig function to load the environment variables:

pnpm add @next/env

npm install @next/env

yarn add @next/env

bun add @next/env

import { loadEnvConfig } from '@next/env'

const projectDir = process.cwd()
loadEnvConfig(projectDir)

import { loadEnvConfig } from '@next/env'

const projectDir = process.cwd()
loadEnvConfig(projectDir)

Then, you can import the configuration where needed. For example:

import './envConfig.ts'

export default defineConfig({
  dbCredentials: {
    connectionString: process.env.DATABASE_URL!,
  },
})

import './envConfig.js'

export default defineConfig({
  dbCredentials: {
    connectionString: process.env.DATABASE_URL,
  },
})

Referencing Other Variables

Next.js will automatically expand variables that use $ to reference other variables e.g. $VARIABLE inside of your .env* files. This allows you to reference other secrets. For example:

TWITTER_USER=nextjs
TWITTER_URL=https://x.com/$TWITTER_USER

In the above example, process.env.TWITTER_URL would be set to https://x.com/nextjs.

Good to know: If you need to use variable with a $ in the actual value, it needs to be escaped e.g. \$.

Bundling Environment Variables for the Browser

Non-NEXT_PUBLIC_ environment variables are only available in the Node.js environment, meaning they aren't accessible to the browser (the client runs in a different environment).

In order to make the value of an environment variable accessible in the browser, Next.js can "inline" a value, at build time, into the js bundle that is delivered to the client, replacing all references to process.env.[variable] with a hard-coded value. To tell it to do this, you just have to prefix the variable with NEXT_PUBLIC_. For example:

NEXT_PUBLIC_ANALYTICS_ID=abcdefghijk

This will tell Next.js to replace all references to process.env.NEXT_PUBLIC_ANALYTICS_ID in the Node.js environment with the value from the environment in which you run next build, allowing you to use it anywhere in your code. It will be inlined into any JavaScript sent to the browser.

Note: After being built, your app will no longer respond to changes to these environment variables. For instance, if you use a Heroku pipeline to promote slugs built in one environment to another environment, or if you build and deploy a single Docker image to multiple environments, all NEXT_PUBLIC_ variables will be frozen with the value evaluated at build time, so these values need to be set appropriately when the project is built. If you need access to runtime environment values, you'll have to setup your own API to provide them to the client (either on demand or during initialization).

import setupAnalyticsService from '../lib/my-analytics-service'

// 'NEXT_PUBLIC_ANALYTICS_ID' can be used here as it's prefixed by 'NEXT_PUBLIC_'.
// It will be transformed at build time to `setupAnalyticsService('abcdefghijk')`.
setupAnalyticsService(process.env.NEXT_PUBLIC_ANALYTICS_ID)

function HomePage() {
  return <h1>Hello World</h1>
}

export default HomePage

Note that dynamic lookups will not be inlined, such as:

// This will NOT be inlined, because it uses a variable
const varName = 'NEXT_PUBLIC_ANALYTICS_ID'
setupAnalyticsService(process.env[varName])

// This will NOT be inlined, because it uses a variable
const env = process.env
setupAnalyticsService(env.NEXT_PUBLIC_ANALYTICS_ID)

Runtime Environment Variables

Next.js can support both build time and runtime environment variables.

By default, environment variables are only available on the server. To expose an environment variable to the browser, it must be prefixed with NEXT_PUBLIC_. However, these public environment variables will be inlined into the JavaScript bundle during next build.

To read runtime environment variables, we recommend using getServerSideProps or incrementally adopting the App Router.

You can safely read environment variables on the server during dynamic rendering:

import { connection } from 'next/server'

export default async function Component() {
  await connection()
  // cookies, headers, and other Request-time APIs
  // will also opt into dynamic rendering, meaning
  // this env variable is evaluated at runtime
  const value = process.env.MY_VALUE
  // ...
}

import { connection } from 'next/server'

export default async function Component() {
  await connection()
  // cookies, headers, and other Request-time APIs
  // will also opt into dynamic rendering, meaning
  // this env variable is evaluated at runtime
  const value = process.env.MY_VALUE
  // ...
}

This allows you to use a singular Docker image that can be promoted through multiple environments with different values.

Good to know:

• You can run code on server startup using the register function.

Test Environment Variables

Apart from development and production environments, there is a 3rd option available: test. In the same way you can set defaults for development or production environments, you can do the same with a .env.test file for the testing environment (though this one is not as common as the previous two). Next.js will not load environment variables from .env.development or .env.production in the testing environment.

This one is useful when running tests with tools like jest or cypress where you need to set specific environment vars only for testing purposes. Test default values will be loaded if NODE_ENV is set to test, though you usually don't need to do this manually as testing tools will address it for you.

There is a small difference between test environment, and both development and production that you need to bear in mind: .env.local won't be loaded, as you expect tests to produce the same results for everyone. This way every test execution will use the same env defaults across different executions by ignoring your .env.local (which is intended to override the default set).

Good to know: similar to Default Environment Variables, .env.test file should be included in your repository, but .env.test.local shouldn't, as .env*.local are intended to be ignored through .gitignore.

While running unit tests you can make sure to load your environment variables the same way Next.js does by leveraging the loadEnvConfig function from the @next/env package.

// The below can be used in a Jest global setup file or similar for your testing set-up
import { loadEnvConfig } from '@next/env'

export default async () => {
  const projectDir = process.cwd()
  loadEnvConfig(projectDir)
}

Environment Variable Load Order

Environment variables are looked up in the following places, in order, stopping once the variable is found.

1. process.env
2. .env.$(NODE_ENV).local
3. .env.local (Not checked when NODE_ENV is test.)
4. .env.$(NODE_ENV)
5. .env

For example, if NODE_ENV is development and you define a variable in both .env.development.local and .env, the value in .env.development.local will be used.

Good to know: The allowed values for NODE_ENV are production, development and test.

Good to know

• If you are using a /src directory, .env.* files should remain in the root of your project.
• If the environment variable NODE_ENV is unassigned, Next.js automatically assigns development when running the next dev command, or production for all other commands.

Version History

Source: docs/01-app/02-guides/environment-variables.mdx