Integrating NextAuth.js
Set up and configure NextAuth.js for easy and secure authentication in your Next.js application.
Integrating NextAuth.js is a free Next.js 15 Fullstack (App Router + Server Actions) lesson on CoddyKit — lesson 1 of 6. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Next.js 15 Fullstack (App Router + Server Actions) learning path, one of 6 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Auth with Next.js 15
Welcome to Integrating NextAuth.js! In modern web applications, user authentication is crucial. It allows users to sign in, proves their identity, and grants them access to personalized content.
Implementing authentication from scratch can be complex and error-prone, involving secure password hashing, session management, and protecting against various attacks.
Introducing NextAuth.js
NextAuth.js (now often referred to as Auth.js) is a complete open-source authentication solution for Next.js applications. It simplifies adding authentication to your project significantly.
- Easy Setup: Get authentication working quickly with minimal configuration.
- Multiple Providers: Supports various authentication methods like Google, GitHub, Email, or custom credentials.
- Secure: Handles many security best practices for you.
- Flexible: Works seamlessly with both Client and Server Components.
Installation
First, let's install the next-auth package in your Next.js project. Open your terminal in the project root and run:
You'll also need to configure environment variables for security and proper functioning.
npm install next-authNextAuth.js Configuration
In Next.js 15 (App Router), NextAuth.js uses a configuration file, typically auth.ts, to define how authentication works. This file exports a configuration object that includes your authentication providers.
You also need to set an environment variable, AUTH_SECRET, which is used to sign and encrypt session tokens. It should be a long, random string.
import NextAuth from "next-auth";
import CredentialsProvider from "next-auth/providers/credentials";
export const { handlers, auth, signIn, signOut } = NextAuth({
providers: [
CredentialsProvider({
name: "Credentials",
credentials: {
username: { label: "Username", type: "text", placeholder: "jsmith" },
password: { label: "Password", type: "password" }
},
async authorize(credentials, req) {
// Logic to verify user credentials
// Return user object if successful, null otherwise
return null;
}
})
],
pages: {
signIn: '/auth/signin',
}
});Credentials Provider
The Credentials Provider allows users to sign in with a username/email and password. You define the input fields (credentials) and provide an authorize function.
The authorize function is where you'll verify the user's input against your database. For this example, we'll use a simple hardcoded check.
import NextAuth from "next-auth";
import CredentialsProvider from "next-auth/providers/credentials";
export const { handlers, auth, signIn, signOut } = NextAuth({
providers: [
CredentialsProvider({
name: "Credentials",
credentials: {
username: { label: "Username", type: "text", placeholder: "test" },
password: { label: "Password", type: "password" }
},
async authorize(credentials) {
if (credentials?.username === "user" && credentials?.password === "pass") {
return { id: "1", name: "Test User", email: "test@example.com" };
}
return null; // Authentication failed
}
})
],
pages: {
signIn: '/auth/signin',
}
});Sign-in Page Component
Now, let's create a client component that provides a sign-in form. We'll use the signIn function exported from our auth.ts file (or next-auth/react if preferred for client components).
This component will handle user input and trigger the authentication flow using the Credentials Provider we configured.
// app/auth/signin/page.tsx (Client Component)
'use client';
import { signIn } from "next-auth/react";
import { useState } from "react";
export default function SignInPage() {
const [username, setUsername] = useState('');
const [password, setPassword] = useState('');
const handleSubmit = async (e: React.FormEvent) => {
e.preventDefault();
const result = await signIn('credentials', {
username,
password,
redirect: false, // Don't redirect automatically
});
if (result?.error) {
alert(result.error);
} else {
window.location.href = '/'; // Redirect on success
}
};
return (
<form onSubmit={handleSubmit}>
<input
type="text"
placeholder="Username (user)"
value={username}
onChange={(e) => setUsername(e.target.value)}
/>
<input
type="password"
placeholder="Password (pass)"
value={password}
onChange={(e) => setPassword(e.target.value)}
/>
<button type="submit">Sign In</button>
</form>
);
}Displaying Session Data
Once a user is signed in, you can access their session information. In Server Components, you can directly use the auth() function from auth.ts to get the session data.
This is great for rendering UI based on the logged-in user or fetching user-specific data on the server.
// app/page.tsx (Server Component)
import { auth, signOut } from "@/auth"; // Adjust path if needed
export default async function HomePage() {
const session = await auth();
return (
<div>
<h1>Welcome!</h1>
{session?.user ? (
<div>
<p>Signed in as {session.user.name || session.user.email}</p>
{/* SignOut button would be in a Client Component */}
</div>
) : (
<p>Not signed in. <a href="/auth/signin">Sign In</a></p>
)}
</div>
);
}Implementing Sign Out
Allowing users to sign out is just as important as signing in. You can use the signOut function from next-auth/react in a Client Component.
When called, signOut clears the user's session and typically redirects them to a specified page (like the homepage or a sign-in page).
// app/components/SignOutButton.tsx (Client Component)
'use client';
import { signOut } from "next-auth/react";
export default function SignOutButton() {
return (
<button onClick={() => signOut({ callbackUrl: '/' })}>
Sign Out
</button>
);
}NextAuth.js Options
NextAuth.js offers many configuration options to customize behavior. In your auth.ts, you can define:
pages: Custom URLs for sign-in, sign-out, error pages.callbacks: Functions to control what happens when a user signs in, updates their session, or creates a JWT.session: Configure session storage (JWT or database).secret: TheAUTH_SECRETenvironment variable.
These options provide powerful control over the authentication flow and user experience.
Quick Check
Which file is primarily used to configure NextAuth.js providers and callbacks in a Next.js 15 App Router project?
Recap & Next Steps
You've successfully learned the basics of integrating NextAuth.js into your Next.js 15 application!
- We installed NextAuth.js.
- Configured
auth.tswith a Credentials Provider. - Created client components for sign-in and sign-out.
- Accessed session data in server components.
In the next lesson, we'll explore how to protect routes and data based on user authentication status using Next.js middleware and server-side checks.
Frequently asked questions
Is the “Integrating NextAuth.js” lesson free?
Yes — the full text of “Integrating NextAuth.js” is free to read here on the web, and the Next.js 15 Fullstack (App Router + Server Actions) course includes 6 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Next.js 15 Fullstack (App Router + Server Actions) course, upgrade to CoddyKit PRO.
What will I learn in “Integrating NextAuth.js”?
Set up and configure NextAuth.js for easy and secure authentication in your Next.js application. You practise Next.js 15 Fullstack (App Router + Server Actions) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Next.js 15 Fullstack (App Router + Server Actions)?
No prior experience is required. Next.js 15 Fullstack (App Router + Server Actions) on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 6, so you can start here or from the beginning and move at your own pace.
How long does the “Integrating NextAuth.js” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Next.js 15 Fullstack (App Router + Server Actions) lesson?
Yes. Every Next.js 15 Fullstack (App Router + Server Actions) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.