clerk-authentication

Clerk Authentication

You are an expert in Clerk authentication implementation for Next.js applications. Follow these guidelines when integrating Clerk.

Core Principles

• Implement defense-in-depth with multiple authentication layers
• Verify authentication at every data access point, not just middleware
• Protect server actions individually
• Use Clerk's built-in security features (HttpOnly cookies, CSRF protection)

Installation and Setup

npm install @clerk/nextjs

Environment Variables

# Required
NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY=pk_...
CLERK_SECRET_KEY=sk_...

# Optional: Custom 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=/dashboard

Provider Setup

App Router (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>
  );
}

With Custom Appearance

import { ClerkProvider } from '@clerk/nextjs';
import { dark } from '@clerk/themes';

export default function RootLayout({ children }: { children: React.ReactNode }) {
  return (
    <ClerkProvider
      appearance={{
        baseTheme: dark,
        variables: {
          colorPrimary: '#3b82f6',
        },
        elements: {
          formButtonPrimary: 'bg-blue-500 hover:bg-blue-600',
        },
      }}
    >
      <html lang="en">
        <body>{children}</body>
      </html>
    </ClerkProvider>
  );
}

Middleware Configuration

Basic Middleware (middleware.ts)

import { clerkMiddleware, createRouteMatcher } from '@clerk/nextjs/server';

// Define protected routes
const isProtectedRoute = createRouteMatcher([
  '/dashboard(.*)',
  '/api/protected(.*)',
  '/settings(.*)',
]);

// Define public routes (optional, for clarity)
const isPublicRoute = createRouteMatcher([
  '/',
  '/sign-in(.*)',
  '/sign-up(.*)',
  '/api/public(.*)',
]);

export default clerkMiddleware(async (auth, req) => {
  if (isProtectedRoute(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)(.*)',
  ],
};