Next.js pass NODE_ENV to client

I’m building a React SSR App, using Next.js.

I want to be able to access the NODE_ENV on the client side, as this will tell my app which API endpoints to use.

I’m struggling to find a decent approach for this. I’d like to define the NODE_ENV as a window variable when I first render the page on the server, and then in my helper function where I make the API call, I would check if the code is being called on the server or the client, and using the window or process.env objects as required.

Does anyone have a good solution for such a problem? It must be a common issue but I can’t find any good solutions.

1. You can include it in webpack configuration (using dotenv-webpack dependency):


const path = require('path')
const Dotenv = require('dotenv-webpack')

module.exports = {
  webpack: (config) => {
    config.plugins = config.plugins || []

    config.plugins = [

      // Read the .env file
      new Dotenv({
        path: path.join(__dirname, '.env'),
        systemvars: true

    return config

Reference: here

2. using babel plugin to import the variable towards the entire app:


const prod = process.env.NODE_ENV === 'production'

module.exports = {
  'process.env.BACKEND_URL': prod ? '' : 'https://localhost:8080'


const env = require('./env-config.js')

module.exports = {
  presets: ['next/babel'],
  plugins: [['transform-define', env]]


export default () => (
  <div>Loading data from { process.env.BACKEND_URL }</div>

Reference: here

3. Using next/config:


module.exports = {
  publicRuntimeConfig: {
    API_URL: process.env.API_URL


import React from 'react'
import getConfig from 'next/config'

const {publicRuntimeConfig} = getConfig()
const {API_URL} = publicRuntimeConfig

export default class extends React.Component {
  static async getInitialProps () {
    // fetch(`${API_URL}/some-path`)
    return {}

  render () {
    return <div>
            The API_URL is {API_URL}

Reference: here

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Using Next’s build-time configuration

@DarrylR already mentioned using next.config.js and
Next’s runtime configuration,
but you can also use Next’s build-time configuration.

This lets you put the process.env.XXXX right into the code (as shown in step 3 below), and you don’t have to import anything. However, if you env variables should be set both when you build locally with Next.js and when you deploy to ZEIT Now, I don’t know if you can keep them in just one file using this method (see step 2 below).

The runtime configuration docs suggest you normally want to use build-time configuration:

Warning: Generally you want to use build-time configuration to provide your configuration. The reason for this is that runtime configuration adds rendering / initialization overhead and is incompatible with automatic prerendering.


1. Set NODE_ENV for build process

1.1 Using ZEIT Now

If you deploy using ZEIT Now, you can set the env variables used at build time in now.json:

  "version": 2,
  "build": {
    "env": {
      "NODE_ENV": "production"

1.2 When running locally (optional)

If you want NODE_ENV to be set when running locally as well, this will not be set by now.json.
However you can set it in other ways, such as:

$ NODE_ENV=production npm run build

or change the build script in package.json to

"build": "NODE_ENV=production next build"

You can of course also set NODE_ENV for other scripts than build if you want that.

2. Make Next inline value of process.env.NODE_ENV

Add this to the next.config.js as described here:

module.exports = {
  env: {
    NODE_ENV: process.env.NODE_ENV

3. Use in code

if (process.env.NODE_ENV === "production") {
  console.log("In production")
} else {
  console.log("Not in production")

Another Easy solution:

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create 2 files on root folder:


inside add variables as you need, for example in .env.development file:


and in .env.production file:


Then use it for example:

console.log('Version: ', process.env.NEXT_PUBLIC_ENV);

Since Next.js 9.4, NextJs has now built-in support for environment variables, which allows you to do the following using .env files:

An example .env.local:


If you want to expose the env variables to the client, you have to prefix the variable with NEXT_PUBLIC_ for example:


If you want to use the variable, you can use it like this: process.env.NEXT_PUBLIC_API_PORT

For the documentation see here

The answers/resolutions are collected from stackoverflow, are licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 .

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