Environment Variables

This document is for Next.js versions 9.4 and up. If you’re using an older version of Next.js, upgrade or refer to Environment Variables in next.config.js.

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

Loading Environment Variables

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

An example .env.local:

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:

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

Exposing Environment Variables to the Browser

By default all environment variables loaded through .env.local are only available in the Node.js environment, meaning they won't be exposed to the browser.

In order to expose a variable to the browser you can prefix the variable with NEXT_PUBLIC_. For example:

NEXT_PUBLIC_ANALYTICS_ID=abcdefghijk

This loads process.env.NEXT_PUBLIC_ANALYTICS_ID into the Node.js environment automatically. Allowing you to use it anywhere in your code. The value will be inlined into JavaScript sent to the browser because of the NEXT_PUBLIC_ prefix.

// pages/index.js
import setupAnalyticsService from '../lib/my-analytics-service'

// NEXT_PUBLIC_ANALYTICS_ID can be used here as it's prefixed by NEXT_PUBLIC_
setupAnalyticsService(process.env.NEXT_PUBLIC_ANALYTICS_ID)

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

export default HomePage

Default Environment Variables

In general only one .env.local file is needed. However, sometimes you might want to add some defaults for the development (next dev) or production (next start) environment.

Next.js allows you to set defaults in .env (all environments), .env.development (development environment), and .env.production (production environment).

.env.local always overrides the defaults set.

Note: .env, .env.development, and .env.production files should be included in your repository as they define defaults. .env*.local should be added to .gitignore, as those files are intended to be ignored. .env.local is where secrets can be stored.

Environment Variables on Vercel

When deploying on Vercel you can configure secrets in the Environment Variables section of the project in the Vercel dashboard.

You can still use .env, .env.development and .env.production to add defaults.

If you've configured Development Environment Variables you can pull them into a .env.local for usage on your local machine using the following command:

vercel env pull .env.local