Clerk Common Errors

Overview

Diagnose and resolve common Clerk authentication errors and issues.

Prerequisites

Clerk SDK installed
Access to Clerk dashboard for configuration checks
Browser developer tools for debugging

Instructions

Error Category 1: Configuration Errors

Invalid API Key

Error: Clerk: Invalid API key

Cause: Publishable or secret key is incorrect or mismatched. Solution:

# Verify keys in .env.local match Clerk dashboard
# Publishable key starts with pk_test_ or pk_live_
# Secret key starts with sk_test_ or sk_live_

# Check for trailing whitespace
cat -A .env.local | grep CLERK

# Ensure correct environment
echo $NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY

ClerkProvider Not Found

Error: useAuth can only be used within the <ClerkProvider /> component

Cause: Component using Clerk hooks is outside ClerkProvider. Solution:

// Ensure ClerkProvider wraps entire app in layout.tsx
import { ClerkProvider } from '@clerk/nextjs'

export default function RootLayout({ children }) {
  return (
    <ClerkProvider>
      <html><body>{children}</body></html>
    </ClerkProvider>
  )
}

Error Category 2: Authentication Errors

Session Not Found

Error: Session not found

Cause: User session expired or was revoked. Solution:

// Handle gracefully in your app
const { userId } = await auth()
if (!userId) {
  redirect('/sign-in')
}

Form Identifier Not Found

Error: form_identifier_not_found

Cause: Email/username not registered. Solution:

// Show helpful message to user
catch (err: any) {
  if (err.errors?.[0]?.code === 'form_identifier_not_found') {
    setError('No account found with this email. Please sign up.')
  }
}

Password Incorrect

Error: form_password_incorrect

Cause: Wrong password entered. Solution:

catch (err: any) {
  if (err.errors?.[0]?.code === 'form_password_incorrect') {
    setError('Incorrect password. Try again or reset your password.')
  }
}

Error Category 3: Middleware Errors

Infinite Redirect Loop

Error: Too many redirects

Cause: Middleware matcher includes sign-in page. Solution:

// middleware.ts
const isPublicRoute = createRouteMatcher([
  '/sign-in(.*)',  // Must include sign-in pages
  '/sign-up(.*)',
  '/'
])

export default clerkMiddleware(async (auth, request) => {
  if (!isPublicRoute(request)) {
    await auth.protect()
  }
})

Middleware Not Executing

Error: Routes not protected

Cause: Matcher not matching routes correctly. Solution:

export const config = {
  matcher: [
    // Skip static files and _next
    '/((?!_next|[^?]*\\.(?:html?|css|js|jpe?g|webp|png|gif|svg|ttf|woff2?|ico)).*)',
    '/',
    '/(api|trpc)(.*)'
  ]
}

Error Category 4: Server/Client Errors

Hydration Mismatch

Error: Text content does not match server-rendered HTML

Cause: Auth state differs between server and client. Solution:

'use client'
import { useUser } from '@clerk/nextjs'

export function UserGreeting() {
  const { user, isLoaded } = useUser()

  // Prevent hydration mismatch by waiting for load
  if (!isLoaded) {
    return <div>Loading...</div>
  }

  return <div>Hello, {user?.firstName}</div>
}

Cannot Read Properties of Undefined

Error: Cannot read properties of undefined (reading 'userId')

Cause: Using auth() in client component or non-server context. Solution:

// Server Component - use auth()
import { auth } from '@clerk/nextjs/server'
const { userId } = await auth()

// Client Component - use useAuth()
'use client'
import { useAuth } from '@clerk/nextjs'
const { userId } = useAuth()

Error Category 5: Webhook Errors

Webhook Verification Failed

Error: Webhook signature verification failed

Cause: Incorrect webhook secret or missing headers. Solution:

// app/api/webhooks/clerk/route.ts
import { Webhook } from 'svix'
import { headers } from 'next/headers'

export async function POST(req: Request) {
  const WEBHOOK_SECRET = process.env.CLERK_WEBHOOK_SECRET!

  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')

  const body = await req.text()

  const wh = new Webhook(WEBHOOK_SECRET)
  const evt = wh.verify(body, {
    'svix-id': svix_id!,
    'svix-timestamp': svix_timestamp!,
    'svix-signature': svix_signature!
  })

  // Process event
}

Output

Identified error category
Root cause analysis
Working solution code

Diagnostic Commands

# Check Clerk version
npm list @clerk/nextjs

# Verify environment variables
npx next info

# Check for multiple Clerk instances
npm list | grep clerk

# Clear Next.js cache
rm -rf .next && npm run dev

Quick Reference Table

Error Code	Meaning	Quick Fix
`form_identifier_not_found`	User doesn't exist	Show sign-up link
`form_password_incorrect`	Wrong password	Show reset link
`session_exists`	Already logged in	Redirect to app
`verification_expired`	Code expired	Resend code
`rate_limit_exceeded`	Too many attempts	Wait and retry

Resources

Next Steps

Proceed to clerk-debug-bundle for comprehensive debugging tools.

clerk-common-errors