If you are seeing the error “process.env is undefined” in a Next.js app, it means that the process.env object is not available in the current context.

The process.env object is a global object that contains environment variables. It is only available on the server-side in a Next.js app, and it is not available in the browser.

If you are trying to access the process.env object on the client-side (e.g., in a browser), you will need to use a different method to access environment variables. One option is to use the next/config module to expose the environment variables to the client-side.

Here’s an example of how you can use the next/config module to access environment variables on the client-side:

import getConfig from 'next/config'

const {publicRuntimeConfig} = getConfig()

console.log(publicRuntimeConfig.API_KEY)

In this example, we are using the getConfig function to get access to the runtime configuration of the app. The publicRuntimeConfig object contains the environment variables that have been exposed to the client-side, and we can access a specific environment variable by its name (e.g., publicRuntimeConfig.API_KEY).

It’s important to note that the next/config module only works in a Next.js app, and it will not work in a traditional Node.js app.

nextjs env variable why start with NEXT_PUBLIC

In a Next.js app, environment variables that start with NEXT_PUBLIC_ are exposed to the client-side of the app. This means that these environment variables can be accessed from the browser using the process.env object or the next/config module.

For example, if you have an environment variable called NEXT_PUBLIC_API_KEY, you can access it on the client-side like this:

console.log(process.env.NEXT_PUBLIC_API_KEY)

Or like this:

import getConfig from 'next/config'

const {publicRuntimeConfig} = getConfig()

console.log(publicRuntimeConfig.NEXT_PUBLIC_API_KEY)

Environment variables that do not start with NEXT_PUBLIC_ are not exposed to the client-side and can only be accessed on the server-side.

The NEXT_PUBLIC_ prefix is a convention used by Next.js to distinguish between environment variables that should be exposed to the client-side and those that should not. It is not required, but it is a good practice to follow to ensure that you don’t accidentally expose sensitive information to the client-side.

nextjs module.exports basePath

In a Next.js app, you can use the basePath property of the module.exports object to specify the base URL for the app. The basePath property is used to set the base path for all of the routes in the app, which can be useful if you are deploying the app to a subdirectory on your server.

Here’s an example of how you can use the basePath property in the next.config.js file:

module.exports = {
    basePath: '/app',
    // other configuration options
}

In this example, we are setting the base path for the app to /app. This means that all of the routes in the app will be prefixed with /app, so the /about route will become /app/about, for example.

It’s important to note that the basePath property only works with the file-system and serverless deployment modes in Next.js. It is not supported in the static deployment mode.