How to set up edge middleware authentication on Vercel
Edge middleware authentication on Vercel is set up by creating a middleware.js file in your project root, configuring authentication logic using JWT or session tokens, and deploying to Vercel's edge runtime. The middleware runs before page requests and can redirect unauthenticated users or validate tokens.
Prerequisites
- A Vercel account with a deployed project
- Basic knowledge of JavaScript and Next.js
- Understanding of authentication concepts
- Node.js installed locally
Step-by-Step Instructions
Create the middleware file
middleware.js or middleware.ts in your project's root directory (same level as pages or app). This file will contain your authentication logic that runs on Vercel's edge runtime before each request is processed.Implement authentication logic
NextRequest and NextResponse APIs. Include token validation, session checking, or cookie verification logic. Use request.nextUrl.clone() to handle redirects and NextResponse.next() to allow authenticated requests to proceed.Configure protected routes
config export with a matcher property. Use patterns like /dashboard/:path* to protect entire sections or specific paths. You can also use conditional logic within the middleware to apply different authentication rules to different routes.Add environment variables
JWT_SECRET, NEXTAUTH_SECRET, or API keys for your authentication provider. These variables will be available in your edge middleware at runtime.Handle authentication responses
NextResponse.redirect() for unauthenticated users, NextResponse.json() for API errors, and NextResponse.next() for successful authentication. Add appropriate headers and status codes for each scenario.Test locally and deploy
npm run dev or yarn dev to ensure authentication flows work correctly. Once tested, commit your changes and push to your connected Git repository. Vercel will automatically deploy your middleware to the edge runtime.Monitor and debug
Common Issues & Troubleshooting
Middleware not executing on certain routes
Check your config.matcher export and ensure the route patterns are correct. Verify that static assets are properly excluded and that your matcher uses the correct regex syntax for Next.js middleware.
Environment variables undefined in middleware
Ensure environment variables are added in the Vercel dashboard under Settings > Environment Variables for all environments. Redeploy your project after adding new variables, as they're not available until the next deployment.
Infinite redirect loops
Check that your middleware doesn't redirect authenticated users to login pages or create circular redirects. Use request.nextUrl.pathname to check the current path and avoid redirecting users who are already on the target page.
Middleware causing performance issues
Minimize external API calls in middleware and use lightweight authentication methods like JWT validation. Consider caching authentication results and avoid heavy computations that can slow down every request to your application.