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)
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.