Next.js Authentication Explained — Auth Patterns and Libraries

DodaTech Updated 2026-06-28 1 min read

In this tutorial, you will learn about Next.js Authentication Explained. We cover key concepts, practical examples, and best practices to help you master this topic.

Next.js authentication integrates with providers like NextAuth.js (Auth.js) for OAuth, credentials, and JWT-based sessions, with middleware for route protection and API auth.

What You'll Learn

Setting up NextAuth.js
OAuth providers (Google, GitHub)
Credentials provider
Session management
Route protection patterns

Why It Matters

Authentication is required for most real-world applications. Next.js middleware handles server-side auth checks at the edge before protected pages render.

// app/api/auth/[...nextauth]/route.js
import NextAuth from "next-auth";
import GoogleProvider from "next-auth/providers/google";
import CredentialsProvider from "next-auth/providers/credentials";

const handler = NextAuth({
  providers: [
    GoogleProvider({
      clientId: process.env.GOOGLE_CLIENT_ID,
      clientSecret: process.env.GOOGLE_CLIENT_SECRET,
    }),
    CredentialsProvider({
      name: "credentials",
      credentials: {
        email: { label: "Email", type: "email" },
        password: { label: "Password", type: "password" },
      },
      async authorize(credentials) {
        const user = await db.authenticate(credentials.email, credentials.password);
        if (user) return { id: user.id, name: user.name, email: user.email };
        return null;
      },
    }),
  ],
  pages: { signIn: "/login" },
  session: { strategy: "jwt" },
  callbacks: {
    async jwt({ token, user }) { return { ...token, ...user }; },
    async session({ session, token }) {
      session.user.id = token.id;
      return session;
    },
  },
});

export { handler as GET, handler as POST };

Expected output: Users can log in via Google OAuth or email/password credentials, with JWT sessions and protected routes via middleware.

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