Authentication in Next.js 15 with Auth.js (NextAuth v5)

Auth.js v5 in Next.js App Router

// auth.ts
import NextAuth from 'next-auth';
import GitHub from 'next-auth/providers/github';

export const { handlers, signIn, signOut, auth } = NextAuth({
    providers: [GitHub],
    callbacks: {
        authorized: async ({ auth }) => {
            return !!auth; // Logged in users can access protected pages
        }
    }
});