})
  // ...
}
Referencing Other Variables
Next.js will automatically expand variables that use $ to reference other variables e.g. $VARIABLE inside of your .env* files. This allows you to reference other secrets. For example:
.env TWITTER_USER=nextjs
TWITTER_URL=https://twitter.com/$TWITTER_USER
In the above example, process.env.TWITTER_URL would be set to https://twitter.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).