How to Add Auth0 to a Next.js Application

Intro

Auth0 is an authentication and authorization platform that provides tools and services for developers to add user authentication to their applications. It offers a variety of features and options for authenticating users, including support for multiple identity providers and protocols.

Additionally, Auth0 provides tools for managing user identities and permissions, as well as analytics and reporting. It is designed to make it easy for developers to add user authentication to their applications, without having to manage the complex underlying infrastructure and security concerns.

To implement Auth0 in a Next.js application, you will need to sign up for a free Auth0 account and create a new application in the Auth0 dashboard. Once you have done this, follow these steps:

Visit the Auth0 website -> https://auth0.com/ and click on the "Sign Up" button in the top right corner of the page.
Enter your email address and create a password for your account.
Click on the "Continue" button to continue.

Follow the rest of the prompts until you successfully create an account.

Install Auth0

Install the auth0-js and next-auth npm packages in your Next.js project by running the following command:

npm install auth0-js next-auth --save

Import Auth0

In your pages/_app.js file, import the initAuth0 function from the next-auth package and call it with your Auth0 client ID, domain, and callback URL as arguments. This will initialize the next-auth library with your Auth0 configuration. Your _app.js file should look something like this:

import App from 'next/app'
import { initAuth0 } from 'next-auth'

const config = {
  clientId: 'your-auth0-client-id',
  domain: 'your-auth0-domain.auth0.com',
  callbackUrl: 'http://localhost:3000/api/auth/callback',
}

class MyApp extends App {
  static async getInitialProps({ Component, ctx }) {
    const { authToken } = await initAuth0(config)(ctx)
    return {
      authToken,
      initialProps: Component.getInitialProps
        ? await Component.getInitialProps(ctx)
        : {},
    }
  }
}

export default MyApp

Import Auth0 handler

In your pages/api/auth/callback.js file, import the handleAuth0 function from the next-auth package and call it with your Auth0 configuration as an argument. This will handle the callback from Auth0 after the user has logged in. Your callback.js file should look something like this:

import { handleAuth0 } from 'next-auth'

const config = {
  clientId: 'your-auth0-client-id',
  domain: 'your-auth0-domain.auth0.com',
  callbackUrl: 'http://localhost:3000/api/auth/callback',
}

export default handleAuth0(config)

In your Next.js application, you can use the useSession hook from the next-auth package to access the user's Auth0 session and check if they are authenticated. Here is an example of how you can use the useSession hook to check if the user is authenticated and render a login button if they are not:

import { useSession } from 'next-auth'

function HomePage() {
  const [session, loading] = useSession()

  if (loading) {
    return <div>Loading...</div>
  }

  return (
    <div>
      {!session && (
        <a href="/api/auth/login">
          <button>Login with Auth0</button>
        </a>
      )}
    </div>
  )
}

export default HomePage

That's it! You have successfully implemented Auth0 in your Next.js application. For more information, you can check out the NextAuth.js documentation at https://next-auth.js.org.

Intro

Sign up for an Auth0 account

Install Auth0

Import Auth0

Import Auth0 handler

Use Auth0 in a login page