next-env

Automatic static (build-time) or runtime environment variables injection for Next.js.
The plugin doesn't handle loading of dotenv files. Use dotenv or dotenv-load.

Installation

npm install --save next-env dotenv-load

or

yarn add next-env dotenv-load

How it works

Your project can consume variables declared in your environment as if they were declared locally in your JS files.
By default any environment variables starting with NEXT_STATIC_ will be embedded in the js bundles on build time. Variables starting with NEXT_PUBLIC_ are injected on runtime (using Next.js publicRuntimeConfig internally). On node-side (SSR) all environment variables are available by default, but it is a good idea to follow the naming convention NEXT_SERVER_.

Usage

Simple

This module exposes a function that allows to configure the plugin.
In your next.config.js:

const nextEnv = require('next-env');
const dotenvLoad = require('dotenv-load');

dotenvLoad();

const withNextEnv = nextEnv();

module.exports = withNextEnv({
  // Your Next.js config.
});

In your .env:

NEXT_SERVER_TEST_1=ONLY_ON_SSR
NEXT_PUBLIC_TEST_1=INJECTED_BY_SSR
NEXT_STATIC_TEST_1=STATIC_TEXT

In your pages/index.js:

export default () => (
  <ul>
    <li>{process.env.NEXT_SERVER_TEST_1}</li>
    <li>{process.env.NEXT_PUBLIC_TEST_1}</li>
    <li>{process.env.NEXT_STATIC_TEST_1}</li>
  </ul>
)

In the above example the output of process.env.NEXT_SERVER_TEST_1 should only be visible until client-side rendering kicks in.

Advanced

In your next.config.js:

const nextEnv = require('next-env');
const dotenvLoad = require('dotenv-load');

dotenvLoad();

const withNextEnv = nextEnv({
  staticPrefix: 'CUSTOM_STATIC_',
  publicPrefix: 'CUSTOM_PUBLIC_',
});

module.exports = withNextEnv({
  // Your Next.js config.
});

In your .env:

CUSTOM_SERVER_TEST_1=ONLY_ON_SSR
CUSTOM_PUBLIC_TEST_1=INJECTED_BY_SSR
CUSTOM_STATIC_TEST_1=STATIC_TEXT

with next-compose-plugins

In your next.config.js:

const withPlugins = require('next-compose-plugins');
const nextEnv = require('next-env');
const dotenvLoad = require('dotenv-load');

dotenvLoad();

const nextConfig = {
  // Your Next.js config.
};

module.exports = withPlugins([

  nextEnv({
    staticPrefix: 'CUSTOM_STATIC_',
    publicPrefix: 'CUSTOM_PUBLIC_',
  }),

  // another plugin with a configuration
  [typescript, {
    typescriptLoaderOptions: {
      transpileOnly: false,
    },
  }],

], nextConfig);