Clerk Authentication
Expert patterns for Clerk auth implementation, middleware, organizations, webhooks, and user sync
Patterns
Next.js App Router Setup
Complete Clerk setup for Next.js 14/15 App Router.
Includes ClerkProvider, environment variables, and basic sign-in/sign-up components.
Key components:
- ClerkProvider: Wraps app for auth context
- <SignIn />, <SignUp />: Pre-built auth forms
- <UserButton />: User menu with session management
Code_example
Environment variables (.env.local)
NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY=pk_test_... CLERK_SECRET_KEY=sk_test_... NEXT_PUBLIC_CLERK_SIGN_IN_URL=/sign-in NEXT_PUBLIC_CLERK_SIGN_UP_URL=/sign-up NEXT_PUBLIC_CLERK_AFTER_SIGN_IN_URL=/dashboard NEXT_PUBLIC_CLERK_AFTER_SIGN_UP_URL=/onboarding
// app/layout.tsx import { ClerkProvider } from '@clerk/nextjs';
export default function RootLayout({ children, }: { children: React.ReactNode; }) { return ( <ClerkProvider> <html lang="en"> <body>{children}</body> </html> </ClerkProvider> ); }
// app/sign-in/[[...sign-in]]/page.tsx import { SignIn } from '@clerk/nextjs';
export default function SignInPage() { return ( <div className="flex justify-center items-center min-h-screen"> <SignIn /> </div> ); }
// app/sign-up/[[...sign-up]]/page.tsx import { SignUp } from '@clerk/nextjs';
export default function SignUpPage() { return ( <div className="flex justify-center items-center min-h-screen"> <SignUp /> </div> ); }
// components/Header.tsx import { SignedIn, SignedOut, SignInButton, UserButton } from '@clerk/nextjs';
export function Header() { return ( <header className="flex justify-between p-4"> <h1>My App</h1> <SignedOut> <SignInButton /> </SignedOut> <SignedIn> <UserButton afterSignOutUrl="/" /> </SignedIn> </header> ); }
Anti_patterns
- Pattern: ClerkProvider inside page component | Why: Provider must wrap entire app in root layout | Fix: Move ClerkProvider to app/layout.tsx
- Pattern: Using auth() without middleware | Why: auth() requires clerkMiddleware to be configured | Fix: Set up middleware.ts with clerkMiddleware
References
- https://clerk.com/docs/nextjs/getting-started/quickstart
Middleware Route Protection
Protect routes using clerkMiddleware and createRouteMatcher.
Best practices:
- Single middleware.ts file at project root
- Use createRouteMatcher for route groups
- auth.protect() for explicit protection
- Centralize all auth logic in middleware
Code_example
// middleware.ts import { clerkMiddleware, createRouteMatcher } from '@clerk/nextjs/server';
// Define protected route patterns const isProtectedRoute = createRouteMatcher([ '/dashboard(.)', '/settings(.)', '/api/private(.*)', ]);
// Define public routes (optional, for clarity) const isPublicRoute = createRouteMatcher([ '/', '/sign-in(.)', '/sign-up(.)', '/api/webhooks(.*)', ]);
export default clerkMiddleware(async (auth, req) => { // Protect matched routes if (isProtectedRoute(req)) { await auth.protect(); } });
export const config = { matcher: [ // Match all routes except static files '/((?!_next|[^?]\\.(?:html?|css|js(?!on)|jpe?g|webp|png|gif|svg|ttf|woff2?|ico|csv|docx?|xlsx?|zip|webmanifest)).)', // Always run for API routes '/(api|trpc)(.*)', ], };
// Advanced: Role-based protection export default clerkMiddleware(async (auth, req) => { if (isProtectedRoute(req)) { await auth.protect(); }
// Admin routes require admin role if (req.nextUrl.pathname.startsWith('/admin')) { await auth.protect({ role: 'org:admin', }); }
// Premium routes require premium permission if (req.nextUrl.pathname.startsWith('/premium')) { await auth.protect({ permission: 'org:premium:access', }); } });
Anti_patterns
- Pattern: Multiple middleware.ts files | Why: Causes conflicts and redirect loops | Fix: Use single middleware.ts with route matchers
- Pattern: Manual redirects in components | Why: Double redirects, missed routes | Fix: Handle all redirects in middleware
- Pattern: Missing matcher config | Why: Middleware won't run on all routes | Fix: Add comprehensive matcher pattern
References
- https://clerk.com/docs/reference/nextjs/clerk-middleware
Server Component Authentication
Access auth state in Server Components using auth() and currentUser().
Key functions:
- auth(): Returns userId, sessionId, orgId, claims
- currentUser(): Returns full User object
- Both require clerkMiddleware to be configured
Code_example
// app/dashboard/page.tsx (Server Component) import { auth, currentUser } from '@clerk/nextjs/server'; import { redirect } from 'next/navigation';
export default async function DashboardPage() { const { userId } = await auth();
if (!userId) { redirect('/sign-in'); }
// Full user data (counts toward rate limits) const user = await currentUser();
return ( <div> <h1>Welcome, {user?.firstName}!</h1> <p>Email: {user?.emailAddresses[0]?.emailAddress}</p> </div> ); }
// Using auth() for quick checks export default async function ProtectedLayout({ children, }: { children: React.ReactNode; }) { const { userId, orgId, orgRole } = await auth();
if (!userId) { redirect('/sign-in'); }
// Check organization access if (!orgId) { redirect('/select-org'); }
return ( <div> <p>Organization Role: {orgRole}</p> {children} </div> ); }
// Server Action with auth check // app/actions/posts.ts 'use server'; import { auth } from '@clerk/nextjs/server';
export async function createPost(formData: FormData) { const { userId } = await auth();
if (!userId) { throw new Error('Unauthorized'); }
const title = formData.get('title') as string;
// Create post with userId const post = await prisma.post.create({ data: { title, authorId: userId, }, });
return post; }
Anti_patterns
- Pattern: Not awaiting auth() | Why: auth() is async in App Router | Fix: Use await auth() or const { userId } = await auth()
- Pattern: Using currentUser() for simple checks | Why: Counts toward rate limits, slower than auth() | Fix: Use auth() for userId checks, currentUser() for user data
References
- https://clerk.com/docs/references/nextjs/auth
Client Component Hooks
Access auth state in Client Components using hooks.
Key hooks:
- useUser(): User object and loading state
- useAuth(): Auth state, signOut, etc.
- useSession(): Session object
- useOrganization(): Current organization
Code_example
// components/UserProfile.tsx 'use client'; import { useUser, useAuth } from '@clerk/nextjs';
export function UserProfile() { const { user, isLoaded, isSignedIn } = useUser(); const { signOut } = useAuth();
if (!isLoaded) { return <div>Loading...</div>; }
if (!isSignedIn) { return <div>Not signed in</div>; }
return ( <div> <img src={user.imageUrl} alt={user.fullName ?? ''} /> <h2>{user.fullName}</h2> <p>{user.emailAddresses[0]?.emailAddress}</p> <button onClick={() => signOut()}>Sign Out</button> </div> ); }
// Organization context 'use client'; import { useOrganization, useOrganizationList } from '@clerk/nextjs';
export function OrgSwitcher() { const { organization, membership } = useOrganization(); const { setActive, userMemberships } = useOrganizationList({ userMemberships: { infinite: true }, });
if (!organization) { return <p>No organization selected</p>; }
return ( <div> <p>Current: {organization.name}</p> <p>Role: {membership?.role}</p>
<select onChange={(e) => setActive?.({ organization: e.target.value })} value={organization.id}
{userMemberships.data?.map((mem) => ( <option key={mem.organization.id} value={mem.organization.id}> {mem.organization.name} </option> ))} </select> </div> ); }
// Protected client component 'use client'; import { useAuth } from '@clerk/nextjs'; import { useRouter } from 'next/navigation'; import { useEffect } from 'react';
export function ProtectedContent() { const { isLoaded, userId } = useAuth(); const router = useRouter();
useEffect(() => { if (isLoaded && !userId) { router.push('/sign-in'); } }, [isLoaded, userId, router]);
if (!isLoaded || !userId) { return <div>Loading...</div>; }
return <div>Protected content here</div>; }
Anti_patterns
- Pattern: Not checking isLoaded | Why: Auth state undefined during hydration | Fix: Always check isLoaded before accessing user/auth state
- Pattern: Using hooks in Server Components | Why: Hooks only work in Client Components | Fix: Use auth() and currentUser() in Server Components
References
- https://clerk.com/docs/references/react/use-user
Organizations and Multi-Tenancy
Implement B2B multi-tenancy with Clerk Organizations.
Features:
- Multiple orgs per user
- Roles and permissions
- Organization-scoped data
- Enterprise SSO per organization
Code_example
// Organization creation UI // app/create-org/page.tsx import { CreateOrganization } from '@clerk/nextjs';
export default function CreateOrgPage() { return ( <div className="flex justify-center"> <CreateOrganization afterCreateOrganizationUrl="/dashboard" /> </div> ); }
// Organization profile and management // app/org-settings/page.tsx import { OrganizationProfile } from '@clerk/nextjs';
export default function OrgSettingsPage() { return <OrganizationProfile />; }
// Organization switcher in header // components/Header.tsx import { OrganizationSwitcher, UserButton } from '@clerk/nextjs';
export function Header() { return ( <header className="flex justify-between p-4"> <OrganizationSwitcher hidePersonal afterCreateOrganizationUrl="/dashboard" afterSelectOrganizationUrl="/dashboard" /> <UserButton /> </header> ); }
// Org-scoped data access // app/dashboard/page.tsx import { auth } from '@clerk/nextjs/server'; import { prisma } from '@/lib/prisma';
export default async function DashboardPage() { const { orgId } = await auth();
if (!orgId) { redirect('/select-org'); }
// Fetch org-scoped data const projects = await prisma.project.findMany({ where: { organizationId: orgId }, });
return ( <div> <h1>Projects</h1> {projects.map((p) => ( <div key={p.id}>{p.name}</div> ))} </div> ); }
// Role-based UI 'use client'; import { useOrganization, Protect } from '@clerk/nextjs';
export function AdminPanel() { const { membership } = useOrganization();
// Using Protect component return ( <Protect role="org:admin" fallback={<p>Admin access required</p>}> <div>Admin content here</div> </Protect> );
// Or manual check if (membership?.role !== 'org:admin') { return <p>Admin access required</p>; }
return <div>Admin content here</div>; }
Anti_patterns
- Pattern: Not scoping data by orgId | Why: Data leaks between organizations | Fix: Always filter queries by orgId from auth()
- Pattern: Hardcoding role strings | Why: Typos cause access issues | Fix: Define role constants or use TypeScript enums
References
- https://clerk.com/docs/guides/organizations
- https://clerk.com/articles/multi-tenancy-in-react-applications-guide
Webhook User Sync
Sync Clerk users to your database using webhooks.
Key webhooks:
- user.created: New user signed up
- user.updated: User profile changed
- user.deleted: User deleted account
Uses svix for signature verification.
Code_example
// app/api/webhooks/clerk/route.ts import { Webhook } from 'svix'; import { headers } from 'next/headers'; import { WebhookEvent } from '@clerk/nextjs/server'; import { prisma } from '@/lib/prisma';
export async function POST(req: Request) { const WEBHOOK_SECRET = process.env.CLERK_WEBHOOK_SECRET;
if (!WEBHOOK_SECRET) { throw new Error('Missing CLERK_WEBHOOK_SECRET'); }
// Get headers const headerPayload = await headers(); const svix_id = headerPayload.get('svix-id'); const svix_timestamp = headerPayload.get('svix-timestamp'); const svix_signature = headerPayload.get('svix-signature');
if (!svix_id || !svix_timestamp || !svix_signature) { return new Response('Missing svix headers', { status: 400 }); }
// Get body const payload = await req.json(); const body = JSON.stringify(payload);
// Verify webhook const wh = new Webhook(WEBHOOK_SECRET); let evt: WebhookEvent;
try { evt = wh.verify(body, { 'svix-id': svix_id, 'svix-timestamp': svix_timestamp, 'svix-signature': svix_signature, }) as WebhookEvent; } catch (err) { console.error('Webhook verification failed:', err); return new Response('Verification failed', { status: 400 }); }
// Handle events const eventType = evt.type;
if (eventType === 'user.created') { const { id, email_addresses, first_name, last_name, image_url } = evt.data;
await prisma.user.create({ data: { clerkId: id, email: email_addresses[0]?.email_address, firstName: first_name, lastName: last_name, imageUrl: image_url, }, }); }
if (eventType === 'user.updated') { const { id, email_addresses, first_name, last_name, image_url } = evt.data;
await prisma.user.update({ where: { clerkId: id }, data: { email: email_addresses[0]?.email_address, firstName: first_name, lastName: last_name, imageUrl: image_url, }, }); }
if (eventType === 'user.deleted') { const { id } = evt.data;
await prisma.user.delete({ where: { clerkId: id! }, }); }
return new Response('Webhook processed', { status: 200 }); }
// Prisma schema // prisma/schema.prisma model User { id String @id @default(cuid()) clerkId String @unique email String @unique firstName String? lastName String? imageUrl String? createdAt DateTime @default(now()) updatedAt DateTime @updatedAt
posts Post[] @@index([clerkId]) }
Anti_patterns
- Pattern: Not verifying webhook signature | Why: Anyone can hit your endpoint with fake data | Fix: Always verify with svix
- Pattern: Blocking middleware for webhook routes | Why: Webhooks come from Clerk, not authenticated users | Fix: Add /api/webhooks(.*)' to public routes
- Pattern: Not handling race conditions | Why: user.created might arrive after user.updated | Fix: Use upsert instead of create, handle missing records
References
- https://clerk.com/docs/webhooks/sync-data
- https://clerk.com/articles/how-to-sync-clerk-user-data-to-your-database
API Route Protection
Protect API routes using auth() from Clerk.
Route Handlers in App Router use auth() for authentication. Middleware provides initial protection, auth() provides in-handler verification.
Code_example
// app/api/projects/route.ts import { auth } from '@clerk/nextjs/server'; import { prisma } from '@/lib/prisma'; import { NextResponse } from 'next/server';
export async function GET() { const { userId, orgId } = await auth();
if (!userId) { return NextResponse.json({ error: 'Unauthorized' }, { status: 401 }); }
// User's personal projects or org projects const projects = await prisma.project.findMany({ where: orgId ? { organizationId: orgId } : { userId, organizationId: null }, });
return NextResponse.json(projects); }
export async function POST(req: Request) { const { userId, orgId } = await auth();
if (!userId) { return NextResponse.json({ error: 'Unauthorized' }, { status: 401 }); }
const body = await req.json();
const project = await prisma.project.create({ data: { name: body.name, userId, organizationId: orgId ?? null, }, });
return NextResponse.json(project, { status: 201 }); }
// Protected with role check // app/api/admin/users/route.ts export async function GET() { const { userId, orgRole } = await auth();
if (!userId) { return NextResponse.json({ error: 'Unauthorized' }, { status: 401 }); }
if (orgRole !== 'org:admin') { return NextResponse.json({ error: 'Forbidden' }, { status: 403 }); }
// Admin-only logic const users = await prisma.user.findMany(); return NextResponse.json(users); }
// Using getAuth in older patterns (not recommended) // For backwards compatibility only import { getAuth } from '@clerk/nextjs/server';
export async function GET(req: Request) { const { userId } = getAuth(req); // ... }
Anti_patterns
- Pattern: Trusting middleware alone | Why: Middleware can be bypassed (CVE-2025-29927) | Fix: Always verify auth in route handler too
- Pattern: Not checking orgId for multi-tenant | Why: Users might access other org's data | Fix: Always filter by orgId from auth()
References
- https://clerk.com/docs/guides/protecting-pages
Sharp Edges
CVE-2025-29927 Middleware Bypass Vulnerability
Severity: CRITICAL
Multiple Middleware Files Cause Conflicts
Severity: HIGH
4KB Session Token Cookie Limit
Severity: HIGH
auth() Requires clerkMiddleware Configuration
Severity: HIGH
Webhook Race Conditions
Severity: MEDIUM
auth() is Async in App Router
Severity: MEDIUM
Middleware Blocks Webhook Endpoints
Severity: MEDIUM
Accessing Auth State Before isLoaded
Severity: MEDIUM
Manual Redirects Cause Double Redirects
Severity: MEDIUM
Organization Data Not Scoped by orgId
Severity: HIGH
Validation Checks
Clerk Secret Key in Client Code
Severity: ERROR
CLERK_SECRET_KEY must only be used server-side
Message: Clerk secret key exposed to client. Use CLERK_SECRET_KEY without NEXT_PUBLIC prefix.
Protected Route Without Middleware
Severity: ERROR
API routes should have middleware protection
Message: API route without auth check. Add middleware protection or auth() check.
Hardcoded Clerk API Keys
Severity: ERROR
Clerk keys should use environment variables
Message: Hardcoded Clerk keys. Use environment variables.
Missing Await on auth()
Severity: ERROR
auth() is async in App Router and must be awaited
Message: auth() not awaited. Use 'await auth()' in App Router.
Multiple Middleware Files
Severity: WARNING
Only one middleware.ts file should exist
Message: Multiple middleware files detected. Use single middleware.ts.
Webhook Route Not Excluded from Protection
Severity: WARNING
Webhook routes should be public
Message: Webhook route may be blocked by middleware. Add to public routes.
Accessing Auth Without isLoaded Check
Severity: WARNING
Check isLoaded before accessing user state in client components
Message: Accessing user without isLoaded check. Check isLoaded first.
Clerk Hooks in Server Component
Severity: ERROR
Clerk hooks only work in Client Components
Message: Clerk hooks in Server Component. Add 'use client' or use auth().
Multi-Tenant Query Without orgId
Severity: WARNING
Organization data should be scoped by orgId
Message: Query without organization scope. Filter by orgId for multi-tenancy.
Webhook Without Signature Verification
Severity: ERROR
Clerk webhooks must verify svix signature
Message: Webhook without signature verification. Use svix to verify.
Collaboration
Delegation Triggers
- user needs database -> postgres-wizard (User table with clerkId)
- user needs payments -> stripe-integration (Customer linked to Clerk user)
- user needs search -> algolia-search (Secured API keys per user)
- user needs analytics -> segment-cdp (User identification)
- user needs email -> resend-email (Transactional emails)
When to Use
- User mentions or implies: adding authentication
- User mentions or implies: clerk auth
- User mentions or implies: user authentication
- User mentions or implies: sign in
- User mentions or implies: sign up
- User mentions or implies: user management
- User mentions or implies: multi-tenancy
- User mentions or implies: organizations
- User mentions or implies: sso
- User mentions or implies: single sign-on
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.
