Authentication Patterns in Next.js Overview

Next.js supports multiple authentication strategies. This skill covers common patterns including NextAuth.js (Auth.js), middleware-based protection, and session management.

Authentication Libraries Library Best For NextAuth.js (Auth.js) Full-featured auth with providers Clerk Managed auth service Lucia Lightweight, flexible auth Supabase Auth Supabase ecosystem Custom JWT Full control NextAuth.js v5 Setup Installation npm install next-auth@beta

Configuration // auth.ts import NextAuth from 'next-auth' import GitHub from 'next-auth/providers/github' import Credentials from 'next-auth/providers/credentials'

export const { handlers, auth, signIn, signOut } = NextAuth({ providers: [ GitHub({ clientId: process.env.GITHUB_ID, clientSecret: process.env.GITHUB_SECRET, }), Credentials({ credentials: { email: { label: 'Email', type: 'email' }, password: { label: 'Password', type: 'password' }, }, authorize: async (credentials) => { const user = await getUserByEmail(credentials.email) if (!user || !verifyPassword(credentials.password, user.password)) { return null } return user }, }), ], callbacks: { authorized: async ({ auth }) => { return !!auth }, }, })

API Route Handler // app/api/auth/[...nextauth]/route.ts import { handlers } from '@/auth'

export const { GET, POST } = handlers

Middleware Protection // middleware.ts export { auth as middleware } from '@/auth'

export const config = { matcher: ['/dashboard/:path', '/api/protected/:path'], }

Getting Session Data In Server Components // app/dashboard/page.tsx import { auth } from '@/auth' import { redirect } from 'next/navigation'

export default async function DashboardPage() { const session = await auth()

if (!session) { redirect('/login') }

return (

Welcome, {session.user?.name}

) }

In Client Components // components/user-menu.tsx 'use client'

import { useSession } from 'next-auth/react'

export function UserMenu() { const { data: session, status } = useSession()

if (status === 'loading') { return

}

if (!session) { return }

return (

{session.user?.name}

) }

Session Provider Setup // app/providers.tsx 'use client'

import { SessionProvider } from 'next-auth/react'

export function Providers({ children }: { children: React.ReactNode }) { return {children} }

// app/layout.tsx import { Providers } from './providers'

export default function RootLayout({ children }) { return ( <html> <body> {children} </body> </html> ) }

export function SignInButton() { return (

) }

export function SignOutButton() { return (

) }

Middleware-Based Auth Basic Pattern // middleware.ts import { NextResponse } from 'next/server' import type { NextRequest } from 'next/server'

const protectedRoutes = ['/dashboard', '/settings', '/api/protected'] const authRoutes = ['/login', '/signup']

export function middleware(request: NextRequest) { const token = request.cookies.get('session')?.value const { pathname } = request.nextUrl

// Redirect authenticated users away from auth pages if (authRoutes.some(route => pathname.startsWith(route))) { if (token) { return NextResponse.redirect(new URL('/dashboard', request.url)) } return NextResponse.next() }

// Protect routes if (protectedRoutes.some(route => pathname.startsWith(route))) { if (!token) { const loginUrl = new URL('/login', request.url) loginUrl.searchParams.set('callbackUrl', pathname) return NextResponse.redirect(loginUrl) } }

return NextResponse.next() }

export const config = { matcher: ['/((?!_next/static|_next/image|favicon.ico).*)'], }

With JWT Verification // middleware.ts import { NextResponse } from 'next/server' import { jwtVerify } from 'jose'

const secret = new TextEncoder().encode(process.env.JWT_SECRET)

export async function middleware(request: NextRequest) { const token = request.cookies.get('token')?.value

if (!token) { return NextResponse.redirect(new URL('/login', request.url)) }

try { const { payload } = await jwtVerify(token, secret) // Token is valid, continue return NextResponse.next() } catch { // Token is invalid return NextResponse.redirect(new URL('/login', request.url)) } }

Role-Based Access Control Extending Session Types // types/next-auth.d.ts import { DefaultSession } from 'next-auth'

declare module 'next-auth' { interface Session { user: { role: 'user' | 'admin' } & DefaultSession['user'] } }

// auth.ts export const { handlers, auth } = NextAuth({ callbacks: { session: ({ session, token }) => ({ ...session, user: { ...session.user, role: token.role, }, }), jwt: ({ token, user }) => { if (user) { token.role = user.role } return token }, }, })

Role-Based Component // components/admin-only.tsx import { auth } from '@/auth' import { redirect } from 'next/navigation'

export async function AdminOnly({ children }: { children: React.ReactNode }) { const session = await auth()

if (session?.user?.role !== 'admin') { redirect('/unauthorized') }

return <>{children}</> }

// Usage export default async function AdminPage() { return ( ) }

Session Storage Options JWT (Stateless) // auth.ts export const { auth } = NextAuth({ session: { strategy: 'jwt' }, // JWT stored in cookies, no database needed })

Database Sessions // auth.ts import { PrismaAdapter } from '@auth/prisma-adapter' import { prisma } from '@/lib/prisma'

export const { auth } = NextAuth({ adapter: PrismaAdapter(prisma), session: { strategy: 'database' }, // Sessions stored in database })

Custom Login Page // app/login/page.tsx 'use client'

import { signIn } from 'next-auth/react' import { useSearchParams } from 'next/navigation'

export default function LoginPage() { const searchParams = useSearchParams() const callbackUrl = searchParams.get('callbackUrl') || '/dashboard'

return (

) }

Security Best Practices Use HTTPS in production Set secure cookie flags (HttpOnly, Secure, SameSite) Implement CSRF protection (built into NextAuth) Validate redirect URLs to prevent open redirects Use environment variables for secrets Implement rate limiting on auth endpoints Hash passwords with bcrypt or argon2 Resources

For detailed patterns, see:

references/middleware-auth.md - Advanced middleware patterns references/session-management.md - Session strategies examples/nextauth-setup.md - Complete NextAuth.js setup

auth-patterns

安装

Welcome, {session.user?.name}