Implementing Authentication in Next.js Using NextAuth.js 2026

What You'll Build

In this tutorial, you'll learn how to implement authentication in a Next.js application using NextAuth.js 2026. By the end of this guide, you'll have a fully functional authentication system where users can sign in using their email or social providers like Google and GitHub. Here's a quick look at what you'll be building:

• A login page where users can choose their preferred sign-in method.
• A secure API route that only authenticated users can access.
• A user profile page displaying user information after successful authentication.

Why This Matters

Authentication is a critical part of many web applications. It ensures that only authorized users can access certain parts of an application, protecting sensitive data and personal information. Implementing authentication can be complex, but NextAuth.js simplifies the process, allowing developers to integrate robust authentication systems with minimal configuration.

When should you use NextAuth.js? If you're developing a Next.js application that requires user authentication, NextAuth.js is a great choice. It's particularly beneficial for:

• Developers who need a quick and reliable authentication solution.
• Applications requiring multiple authentication providers.
• Projects where maintaining a custom authentication system would be too resource-intensive.

Architecture Overview

NextAuth.js integrates seamlessly with Next.js, leveraging its API routes to handle authentication. Here's a simple breakdown of the architecture:

+-------------------+       +--------------------+
|   Client (Next.js) | <---> | NextAuth API Routes |
+-------------------+       +--------------------+
          |                           |
          |                           |
          v                           v
  Authentication Providers       Database (optional)
    (Google, GitHub, etc.)

• Client (Next.js): The frontend of your application where users interact with the UI.
• NextAuth API Routes: Server-side logic handling the authentication process.
• Authentication Providers: External services like Google or GitHub for user authentication.
• Database (optional): Used for storing user sessions and data if needed.

Step-by-Step Implementation

Let's dive into the implementation. We'll start by setting up a new Next.js project and integrating NextAuth.js.

1. Set Up a New Next.js Project

First, create a new Next.js project. If you haven't already, ensure you have Node.js and npm installed on your machine. Then run the following command:

npx create-next-app@latest next-auth-tutorial

Navigate into your project directory:

cd next-auth-tutorial

This command sets up a new Next.js application with all the necessary files and dependencies. You should see a folder structure like this:

next-auth-tutorial/
├── pages/
│   ├── api/
│   ├── _app.js
│   └── index.js
├── public/
├── styles/
├── .gitignore
├── package.json
└── README.md

2. Install NextAuth.js

Now, let's install NextAuth.js and its peer dependencies. Run the following command:

npm install next-auth

NextAuth.js requires a few additional packages to function correctly. Make sure you also have next and react installed, which should already be present if you used create-next-app.

3. Configure NextAuth.js

Next, you'll need to configure NextAuth.js in your application. Create a new file named [...nextauth].js inside the pages/api/auth directory:

mkdir -p pages/api/auth
touch pages/api/auth/[...nextauth].js

In [...nextauth].js, set up the NextAuth configuration. Here's a basic example using Google and GitHub as providers:

// pages/api/auth/[...nextauth].js
import NextAuth from "next-auth";
import GoogleProvider from "next-auth/providers/google";
import GitHubProvider from "next-auth/providers/github";

export default NextAuth({
  providers: [
    GoogleProvider({
      clientId: process.env.GOOGLE_CLIENT_ID,
      clientSecret: process.env.GOOGLE_CLIENT_SECRET,
    }),
    GitHubProvider({
      clientId: process.env.GITHUB_CLIENT_ID,
      clientSecret: process.env.GITHUB_CLIENT_SECRET,
    }),
  ],
  // Add more configuration options here
});

• GoogleProvider and GitHubProvider: These are the authentication providers. You'll need to set up OAuth credentials with Google and GitHub to get the clientId and clientSecret.
• Environment Variables: Store sensitive information like clientId and clientSecret in environment variables for security. Create a .env.local file in the root of your project to store these variables:

# .env.local
GOOGLE_CLIENT_ID=your-google-client-id
GOOGLE_CLIENT_SECRET=your-google-client-secret
GITHUB_CLIENT_ID=your-github-client-id
GITHUB_CLIENT_SECRET=your-github-client-secret

Now, your Next.js application is set up with NextAuth.js, ready to handle authentication with Google and GitHub. In the next steps, we'll create a login page and protect routes to ensure only authenticated users can access certain parts of your application.

4. Create a Login Page

Next, let's create a login page where users can choose their preferred sign-in method. In your pages directory, create a new file named login.js:

// pages/login.js
import { signIn } from "next-auth/react";

export default function Login() {
  return (
    <div>
      <h1>Sign In</h1>
      <button onClick={() => signIn("google")}>Sign in with Google</button>
      <button onClick={() => signIn("github")}>Sign in with GitHub</button>
    </div>
  );
}

• signIn Function: This is provided by NextAuth.js and is used to initiate the sign-in process with the specified provider.

5. Protect Routes

To ensure that only authenticated users can access certain pages, you'll need to protect these routes. Let's create a profile page that only authenticated users can view. Create a new file named profile.js in the pages directory:

// pages/profile.js
import { useSession, signOut } from "next-auth/react";

export default function Profile() {
  const { data: session, status } = useSession();

  if (status === "loading") {
    return <p>Loading...</p>;
  }

  if (!session) {
    return <p>You are not logged in.</p>;
  }

  return (
    <div>
      <h1>Profile</h1>
      <p>Welcome, {session.user.name}!</p>
      <button onClick={() => signOut()}>Sign Out</button>
    </div>
  );
}

• useSession Hook: This hook retrieves the current authentication session.
• signOut Function: Provided by NextAuth.js, it logs the user out.

6. Update Navigation and Test

Finally, update your navigation to include links to the login and profile pages. Open pages/index.js and modify it as follows:

// pages/index.js
import Link from "next/link";

export default function Home() {
  return (
    <div>
      <h1>Home Page</h1>
      <nav>
        <Link href="/login">Login</Link>
        <Link href="/profile">Profile</Link>
      </nav>
    </div>
  );
}

Run your Next.js application using:

npm run dev

Visit http://localhost:3000 to test the login and profile pages. Ensure you can log in with Google and GitHub and that the profile page is accessible only when logged in.

Common Mistakes

1. Missing Environment Variables: Ensure that .env.local is correctly configured and that your environment variables are loaded. Missing or incorrect values will prevent authentication.

2. OAuth Credentials: Double-check your OAuth credentials in the Google and GitHub developer consoles. Incorrect credentials will lead to authentication errors.

3. Session Management: If the session is not persisting, verify that your next-auth configuration is correct and that your browser allows cookies.

How I Would Use This

Implementing authentication with NextAuth.js is ideal for small to medium-sized applications requiring multiple authentication providers. It simplifies authentication and reduces the need for custom solutions.

• When to Use: For projects where rapid setup and multiple provider support are priorities.
• When to Avoid: If your application requires complex authentication flows or custom logic not supported by NextAuth.js, consider alternatives or custom implementations.
• Production Considerations: Ensure proper environment configurations and secure handling of secrets. Regularly update dependencies to mitigate security vulnerabilities.
• Cost and Maintenance: NextAuth.js is open-source and free, but consider potential costs associated with third-party providers.

Lessons Learned

• Tradeoffs: NextAuth.js provides convenience at the cost of flexibility. Custom requirements might necessitate additional configuration or alternative solutions.
• Unexpected Issues: OAuth configuration can be tricky, especially with provider-specific nuances. Thoroughly read provider documentation.
• Real-World Considerations: Monitor authentication performance and user experience, especially if your app scales significantly.

Next Steps

1. Explore Database Integration: Learn how to integrate a database with NextAuth.js for storing user sessions and additional user data.
2. Advanced Customization: Dive into customizing the NextAuth.js callbacks and events to tailor authentication flows to your needs.
3. Security Best Practices: Study best practices for securing authentication in web applications to enhance your implementation.

Sources

• NextAuth.js Documentation
• Next.js Documentation
• Google Developer Console
• GitHub Developer Settings