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Building Full Stack Web Applications with Next.js

End-to-End Authentication with NextAuth.js

Explore how to implement secure authentication in Next.js using NextAuth.js, covering OAuth provider integration, client and server session management, protected routes, and best practices for user sign-in and sign-out. This lesson helps you build a robust, industry-standard authentication system for full stack applications.

We'll cover the following...

In this lesson, we’ll transition from basic routing concepts to implementing essential security that protects everything in our app. We‘ll use NextAuth.js (now a part of the larger Auth.js project), which has become the industry-standard solution for Next.js. NextAuth.js provides a streamlined way to handle the complex parts of authentication, such as session management and credential handling.

Why NextAuth.js

We could try to build an authentication system from scratch, but we’d quickly run into the complexities of modern security. We’d need to correctly implement social login flows, securely manage session cookies with the right flags (HttpOnly, SameSite, and Secure), handle JSON Web Tokens (JWTs), and protect against common vulnerabilities like Cross-Site Request Forgery (CSRF).

NextAuth.js addresses these challenges by providing an open-source solution that abstracts many of the underlying authentication details. It supports core Next.js features, including Server Components, Server Actions, and the Proxy, ensuring alignment with the framework’s recommended patterns.

What’s a “provider”?

Before we write any code, let’s clarify a key concept: a provider is simply a service that can verify a user’s identity for you. This is done using OAuth (Open Authorization), an open standard that allows one application (ours) to get limited information from another (like GitHub) on behalf of a user, without them having to share their password.

When a user clicks “Sign in with GitHub,” the flow enabled by the OAuth protocol looks like this:

  1. We send the user to GitHub.

  2. The user logs into GitHub (if they aren’t already).

  3. GitHub asks them, “Do you approve this app to see your public profile?”

  4. If they click “Approve,” GitHub sends them back to our app with a secure, temporary token that says, “This person is legit. Here’s their name and email.”

This is free to use. We simply register our application with the provider (like GitHub) to receive a unique Client ID and Client Secret, which are keys that allow our app to communicate with the provider securely. ...