Clerk Install & Auth
Overview
Set up Clerk SDK and configure authentication for Next.js, React, or Express. This skill covers SDK installation, environment variables, ClerkProvider, middleware, and initial auth verification.
Prerequisites
- Node.js 18+
- Package manager (npm, pnpm, or yarn)
- Clerk account at dashboard.clerk.com
- Publishable Key (
pk_test_*) and Secret Key (sk_test_*) from Clerk Dashboard > API Keys
Instructions
Step 1: Install SDK for Your Framework
set -euo pipefail
# Next.js (App Router or Pages Router)
npm install @clerk/nextjs
# React SPA (Vite, CRA, etc.)
npm install @clerk/clerk-react
# Express / Node.js backend
npm install @clerk/express
# Backend-only (Cloudflare Workers, serverless, etc.)
npm install @clerk/backendStep 2: Configure Environment Variables
# .env.local — never commit this file
NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY=pk_test_...
CLERK_SECRET_KEY=sk_test_...
# Optional: routing URLs
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=/onboardingEnsure .env.local is in .gitignore:
echo ".env.local" >> .gitignoreStep 3: Add ClerkProvider (Next.js App Router)
// app/layout.tsx
import { ClerkProvider, SignInButton, SignedIn, SignedOut, UserButton } from '@clerk/nextjs'
import './globals.css'
export default function RootLayout({ children }: { children: React.ReactNode }) {
return (
<ClerkProvider>
<html lang="en">
<body>
<header className="flex justify-between p-4">
<SignedOut>
<SignInButton />
</SignedOut>
<SignedIn>
<UserButton />
</SignedIn>
</header>
{children}
</body>
</html>
</ClerkProvider>
)
}Step 4: Add Middleware
// middleware.ts (project root, NOT inside app/ or src/app/)
import { clerkMiddleware, createRouteMatcher } from '@clerk/nextjs/server'
// Define which routes should be publicly accessible
const isPublicRoute = createRouteMatcher([
'/',
'/sign-in(.*)',
'/sign-up(.*)',
'/api/webhooks(.*)',
])
export default clerkMiddleware(async (auth, req) => {
if (!isPublicRoute(req)) {
await auth.protect()
}
})
export const config = {
matcher: [
// Skip Next.js internals and 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)(.*)',
],
}Step 5: Create Sign-In and Sign-Up Pages
// app/sign-in/[[...sign-in]]/page.tsx
import { SignIn } from '@clerk/nextjs'
export default function SignInPage() {
return (
<div className="flex min-h-screen items-center justify-center">
<SignIn />
</div>
)
}// app/sign-up/[[...sign-up]]/page.tsx
import { SignUp } from '@clerk/nextjs'
export default function SignUpPage() {
return (
<div className="flex min-h-screen items-center justify-center">
<SignUp />
</div>
)
}Step 6: Verify Connection
// app/api/health/route.ts
import { auth } from '@clerk/nextjs/server'
export async function GET() {
const { userId } = await auth()
return Response.json({
clerkConnected: true,
authenticated: !!userId,
userId: userId || null,
})
}React SPA Setup (Vite)
// src/main.tsx
import { ClerkProvider } from '@clerk/clerk-react'
import App from './App'
const PUBLISHABLE_KEY = import.meta.env.VITE_CLERK_PUBLISHABLE_KEY
if (!PUBLISHABLE_KEY) {
throw new Error('Missing VITE_CLERK_PUBLISHABLE_KEY in .env')
}
ReactDOM.createRoot(document.getElementById('root')!).render(
<ClerkProvider publishableKey={PUBLISHABLE_KEY}>
<App />
</ClerkProvider>
)Express Setup
// server.ts
import express from 'express'
import { clerkMiddleware, requireAuth, getAuth } from '@clerk/express'
const app = express()
// Apply Clerk middleware globally — attaches auth to all requests
app.use(clerkMiddleware())
// Public route
app.get('/api/health', (req, res) => {
res.json({ status: 'ok' })
})
// Protected route — redirects unauthenticated requests
app.get('/api/profile', requireAuth(), (req, res) => {
const { userId } = getAuth(req)
res.json({ userId })
})
app.listen(3001, () => console.log('Server running on :3001'))Error Handling
| Error | Cause | Solution |
|---|---|---|
Missing publishableKey | Env var not set | Add NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY to .env.local |
ClerkProvider must wrap your application | Hook used outside provider | Ensure ClerkProvider wraps root layout |
auth() was called but Clerk can't detect clerkMiddleware() | Middleware not running | Place middleware.ts at project root, check matcher |
Module not found: @clerk/nextjs | Package not installed | Run npm install @clerk/nextjs |
| 500 error on all pages | CLERK_SECRET_KEY missing or wrong | Verify key prefix matches environment (sk_test_ for dev) |
Enterprise Considerations
- Use separate Clerk instances per environment (dev/staging/prod)
- Store keys in platform secrets (Vercel, AWS Secrets Manager), never in
.envfiles committed to git - The
CLERK_SECRET_KEYmust never be exposed client-side; onlyNEXT_PUBLIC_CLERK_PUBLISHABLE_KEYis safe for browsers - For monorepos, install
@clerk/nextjsonly in the app that needs it; use@clerk/backendfor shared server packages - Enable Clerk's "Enhanced email deliverability" in production for reliable transactional emails
Resources
Next Steps
Proceed to clerk-hello-world for your first authenticated request.