Environment Variables

Since the release of Next.js 9.4 we now have a more intuitive and ergonomic experience for adding environment variables. Give it a try!


Note: environment variables specified in this way will always be included in the JavaScript bundle, prefixing the environment variable name with NEXT_PUBLIC_ only has an effect when specifying them through the environment or .env files.

To add environment variables to the JavaScript bundle, open next.config.js and add the env config:

module.exports = {
  env: {
    customKey: 'my-value',

Now you can access process.env.customKey in your code. For example:

function Page() {
  return <h1>The value of customKey is: {process.env.customKey}</h1>

export default Page

Next.js will replace process.env.customKey with 'my-value' at build time. Trying to destructure process.env variables won't work due to the nature of webpack DefinePlugin.

For example, the following line:

return <h1>The value of customKey is: {process.env.customKey}</h1>

Will end up being:

return <h1>The value of customKey is: {'my-value'}</h1>