Next.js + Supabase Auth
Expert integration of Supabase Auth with Next.js App Router
Capabilities
- nextjs-auth
- supabase-auth-nextjs
- auth-middleware
- auth-callback
Prerequisites
- Required skills: nextjs-app-router, supabase-backend
Patterns
Supabase Client Setup
Create properly configured Supabase clients for different contexts
When to use: Setting up auth in a Next.js project
// lib/supabase/client.ts (Browser client) 'use client' import { createBrowserClient } from '@supabase/ssr'
export function createClient() { return createBrowserClient( process.env.NEXT_PUBLIC_SUPABASE_URL!, process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY! ) }
// lib/supabase/server.ts (Server client) import { createServerClient } from '@supabase/ssr' import { cookies } from 'next/headers'
export async function createClient() { const cookieStore = await cookies() return createServerClient( process.env.NEXT_PUBLIC_SUPABASE_URL!, process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!, { cookies: { getAll() { return cookieStore.getAll() }, setAll(cookiesToSet) { cookiesToSet.forEach(({ name, value, options }) => { cookieStore.set(name, value, options) }) }, }, } ) }
Auth Middleware
Protect routes and refresh sessions in middleware
When to use: You need route protection or session refresh
// middleware.ts import { createServerClient } from '@supabase/ssr' import { NextResponse, type NextRequest } from 'next/server'
export async function middleware(request: NextRequest) { let response = NextResponse.next({ request })
const supabase = createServerClient( process.env.NEXT_PUBLIC_SUPABASE_URL!, process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!, { cookies: { getAll() { return request.cookies.getAll() }, setAll(cookiesToSet) { cookiesToSet.forEach(({ name, value, options }) => { response.cookies.set(name, value, options) }) }, }, } )
// Refresh session if expired const { data: { user } } = await supabase.auth.getUser()
// Protect dashboard routes if (request.nextUrl.pathname.startsWith('/dashboard') && !user) { return NextResponse.redirect(new URL('/login', request.url)) }
return response }
export const config = { matcher: ['/((?!_next/static|_next/image|favicon.ico).*)'], }
Auth Callback Route
Handle OAuth callback and exchange code for session
When to use: Using OAuth providers (Google, GitHub, etc.)
// app/auth/callback/route.ts import { createClient } from '@/lib/supabase/server' import { NextResponse } from 'next/server'
export async function GET(request: Request) { const { searchParams, origin } = new URL(request.url) const code = searchParams.get('code') const next = searchParams.get('next') ?? '/'
if (code) {
const supabase = await createClient()
const { error } = await supabase.auth.exchangeCodeForSession(code)
if (!error) {
return NextResponse.redirect(${origin}${next})
}
}
return NextResponse.redirect(${origin}/auth/error)
}
Server Action Auth
Handle auth operations in Server Actions
When to use: Login, logout, or signup from Server Components
// app/actions/auth.ts 'use server' import { createClient } from '@/lib/supabase/server' import { redirect } from 'next/navigation' import { revalidatePath } from 'next/cache'
export async function signIn(formData: FormData) { const supabase = await createClient() const { error } = await supabase.auth.signInWithPassword({ email: formData.get('email') as string, password: formData.get('password') as string, })
if (error) { return { error: error.message } }
revalidatePath('/', 'layout') redirect('/dashboard') }
export async function signOut() { const supabase = await createClient() await supabase.auth.signOut() revalidatePath('/', 'layout') redirect('/') }
Get User in Server Component
Access the authenticated user in Server Components
When to use: Rendering user-specific content server-side
// app/dashboard/page.tsx import { createClient } from '@/lib/supabase/server' import { redirect } from 'next/navigation'
export default async function DashboardPage() { const supabase = await createClient() const { data: { user } } = await supabase.auth.getUser()
if (!user) { redirect('/login') }
return ( Welcome, {user.email} ) }
Validation Checks
Using getSession() for Auth Checks
Severity: ERROR
Message: getSession() doesn't verify the JWT. Use getUser() for secure auth checks.
Fix action: Replace getSession() with getUser() for security-critical checks
OAuth Without Callback Route
Severity: ERROR
Message: Using OAuth but missing callback route at app/auth/callback/route.ts
Fix action: Create app/auth/callback/route.ts to handle OAuth redirects
Browser Client in Server Context
Severity: ERROR
Message: Browser client used in server context. Use createServerClient instead.
Fix action: Import and use createServerClient from @supabase/ssr
Protected Routes Without Middleware
Severity: WARNING
Message: No middleware.ts found. Consider adding middleware for route protection.
Fix action: Create middleware.ts to protect routes and refresh sessions
Hardcoded Auth Redirect URL
Severity: WARNING
Message: Hardcoded localhost redirect. Use origin for environment flexibility.
Fix action: Use window.location.origin or process.env.NEXT_PUBLIC_SITE_URL
Auth Call Without Error Handling
Severity: WARNING
Message: Auth operation without error handling. Always check for errors.
Fix action: Destructure { data, error } and handle error case
Auth Action Without Revalidation
Severity: WARNING
Message: Auth action without revalidatePath. Cache may show stale auth state.
Fix action: Add revalidatePath('/', 'layout') after auth operations
Client-Only Route Protection
Severity: WARNING
Message: Client-side route protection shows flash of content. Use middleware.
Fix action: Move protection to middleware.ts for better UX
Collaboration
Delegation Triggers
- database|rls|queries|tables -> supabase-backend (Auth needs database layer)
- route|page|component|layout -> nextjs-app-router (Auth needs Next.js patterns)
- deploy|production|vercel -> vercel-deployment (Auth needs deployment config)
- ui|form|button|design -> frontend (Auth needs UI components)
Full Auth Stack
Skills: nextjs-supabase-auth, supabase-backend, nextjs-app-router, vercel-deployment
Workflow:
1. Database setup (supabase-backend)
2. Auth implementation (nextjs-supabase-auth)
3. Route protection (nextjs-app-router)
4. Deployment config (vercel-deployment)
Protected SaaS
Skills: nextjs-supabase-auth, stripe-integration, supabase-backend
Workflow:
1. User authentication (nextjs-supabase-auth)
2. Customer sync (stripe-integration)
3. Subscription gating (supabase-backend)
Related Skills
Works well with: nextjs-app-router, supabase-backend
When to Use
- User mentions or implies: supabase auth next
- User mentions or implies: authentication next.js
- User mentions or implies: login supabase
- User mentions or implies: auth middleware
- User mentions or implies: protected route
- User mentions or implies: auth callback
- User mentions or implies: session management
Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.