SKILL.md

Auth0 Next.js Integration

Name: auth0-nextjs
Author: auth0

Add authentication to Next.js applications using @auth0/nextjs-auth0. Supports both App Router and Pages Router.

Prerequisites

Next.js 13+ application (App Router or Pages Router)

Auth0 account and application configured

If you don't have Auth0 set up yet, use the auth0-quickstart skill first

When NOT to Use

Client-side only React apps - Use auth0-react for Vite/CRA SPAs

React Native mobile apps - Use auth0-react-native for iOS/Android

Non-Next.js frameworks - Use framework-specific SDKs (Express, Vue, Angular, etc.)

Stateless APIs only - Use JWT validation middleware if you don't need session management

Quick Start Workflow

1. Install SDK

npm install @auth0/nextjs-auth0

2. Configure Environment

For automated setup with Auth0 CLI, see Setup Guide for complete scripts.

For manual setup:

Create .env.local:

AUTH0_SECRET=<generate-a-32-character-secret>

APP_BASE_URL=http://localhost:3000

AUTH0_DOMAIN=your-tenant.auth0.com

AUTH0_CLIENT_ID=your-client-id

AUTH0_CLIENT_SECRET=your-client-secret

Generate secret: openssl rand -hex 32

Important: Add .env.local to .gitignore

3. Create Auth0 Client and Middleware

Detect project structure first: Check whether the project uses a src/ directory (i.e. src/app/ or src/pages/ exists). This determines where to place files:

**With src/:** src/lib/auth0.ts, src/middleware.ts (or src/proxy.ts for Next.js 16)

**Without src/:** lib/auth0.ts, middleware.ts (or proxy.ts for Next.js 16)

Create lib/auth0.ts (or src/lib/auth0.ts if using the src/ convention):

import { Auth0Client } from '@auth0/nextjs-auth0/server';

export const auth0 = new Auth0Client({

  domain: process.env.AUTH0_DOMAIN!,

  clientId: process.env.AUTH0_CLIENT_ID!,

  clientSecret: process.env.AUTH0_CLIENT_SECRET!,

  secret: process.env.AUTH0_SECRET!,

  appBaseUrl: process.env.APP_BASE_URL!,

});

Middleware Configuration (Next.js 15 vs 16):

Next.js 15 - Create middleware.ts (at project root, or src/middleware.ts if using src/):

import { NextRequest } from 'next/server';

import { auth0 } from '@/lib/auth0';

export async function middleware(request: NextRequest) {

  return await auth0.middleware(request);

}

export const config = {

  matcher: [

    '/((?!_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt).*)',

  ],

};

Next.js 16 - You have two options:

Option 1: Use middleware.ts (same as Next.js 15, same src/ placement rules):

import { NextRequest } from 'next/server';

import { auth0 } from '@/lib/auth0';

export async function middleware(request: NextRequest) {

  return await auth0.middleware(request);

}

export const config = {

  matcher: [

    '/((?!_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt).*)',

  ],

};

Option 2: Use proxy.ts (at project root, or src/proxy.ts if using src/):

import { NextRequest } from 'next/server';

import { auth0 } from '@/lib/auth0';

export async function proxy(request: NextRequest) {

  return await auth0.middleware(request);

}

export const config = {

  matcher: [

    '/((?!_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt).*)',

  ],

};

This automatically creates endpoints:

/auth/login - Login

/auth/logout - Logout

/auth/callback - OAuth callback

/auth/profile - User profile

4. Add User Context (Optional)

Note: In v4, wrapping with <Auth0Provider> is optional. Only needed if you want to pass an initial user during server rendering to useUser().

App Router - Optionally wrap app in app/layout.tsx:

import { Auth0Provider } from '@auth0/nextjs-auth0/client';

import { auth0 } from '@/lib/auth0';

export default async function RootLayout({ children }: { children: React.ReactNode }) {

  const session = await auth0.getSession();

  return (

    <html>

      <body>

        <Auth0Provider user={session?.user}>{children}</Auth0Provider>

      </body>

    </html>

  );

}

Pages Router - Optionally wrap app in pages/_app.tsx:

import { Auth0Provider } from '@auth0/nextjs-auth0/client';

import type { AppProps } from 'next/app';

export default function App({ Component, pageProps }: AppProps) {

  return (

    <Auth0Provider user={pageProps.user}>

      <Component {...pageProps} />

    </Auth0Provider>

  );

}

5. Add Authentication UI

Client Component (works in both routers):

'use client'; // Only needed for App Router

import { useUser } from '@auth0/nextjs-auth0/client';

export default function Profile() {

  const { user, isLoading } = useUser();

  if (isLoading) return <div>Loading...</div>;

  if (user) {

    return (

      <div>

        <img src={user.picture} alt={user.name} />

        <h2>Welcome, {user.name}!</h2>

        <a href="/auth/logout">Logout</a>

      </div>

    );

  }

  return <a href="/auth/login">Login</a>;

}

6. Test Authentication

Start your dev server:

npm run dev

Visit http://localhost:3000 and test the login flow.

Detailed Documentation

Setup Guide - Automated setup scripts, environment configuration, Auth0 CLI usage

Integration Guide - Server-side auth, protected routes, API routes, middleware

API Reference - Complete SDK API, hooks, helpers, session management

Common Mistakes

Mistake

Fix

Using v3 environment variables

v4 uses APP_BASE_URL and AUTH0_DOMAIN (not AUTH0_BASE_URL or AUTH0_ISSUER_BASE_URL)

Forgot to add callback URL in Auth0 Dashboard

Add /auth/callback to Allowed Callback URLs (e.g., http://localhost:3000/auth/callback)

Missing middleware configuration

v4 requires middleware to mount auth routes - create middleware.ts (Next.js 15+16) or proxy.ts (Next.js 16 only) with auth0.middleware()

Wrong route paths

v4 uses /auth/login not /api/auth/login - routes drop the /api prefix

Missing or weak AUTH0_SECRET

Generate secure secret with openssl rand -hex 32 and store in .env.local

Using .env instead of .env.local

Next.js requires .env.local for local secrets, and .env.local should be in .gitignore

App created as SPA type in Auth0

Must be Regular Web Application type for Next.js

Using removed v3 helpers

v4 removed withPageAuthRequired and withApiAuthRequired - use getSession() instead

Using useUser in Server Component

useUser is client-only, use auth0.getSession() for Server Components

AUTH0_DOMAIN includes https://

v4 AUTH0_DOMAIN should be just the domain (e.g., example.auth0.com), no scheme

Related Skills

auth0-quickstart - Basic Auth0 setup

auth0-migration - Migrate from another auth provider

auth0-mfa - Add Multi-Factor Authentication

auth0-cli - Manage Auth0 resources from the terminal

Quick Reference

V4 Setup:

Detect src/ convention: check if src/app/ or src/pages/ exists — place all files inside src/ if so

Create lib/auth0.ts (or src/lib/auth0.ts) with Auth0Client instance

Create middleware configuration (required):

Next.js 15: middleware.ts (or src/middleware.ts) with middleware() function

Next.js 16: middleware.ts with middleware() OR proxy.ts with proxy() function (same src/ rules)

Optional: Wrap with <Auth0Provider> for SSR user

Client-Side Hooks:

useUser() - Get user in client components

user - User profile object

isLoading - Loading state

Server-Side Methods:

auth0.getSession() - Get session in Server Components/API routes/middleware

auth0.getAccessToken() - Get access token for calling APIs

Common Use Cases:

Protected pages (App Router) → Integration Guide

Protected pages (Pages Router) → Integration Guide

API routes with auth → Integration Guide

Middleware protection → Integration Guide

References

Auth0 Next.js SDK Documentation

Auth0 Next.js Quickstart

SDK GitHub Repository

auth0-nextjs