vercel.json redirects and Next.js middleware path conflicts

Answer to the question

In a production build on Vercel, the edge network applies the vercel.json redirects (and rewrites) before invoking any middleware.ts code. If a request matches a redirect rule, Vercel immediately sends the redirect response (typically a 308) and skips the middleware entirely. This is the opposite of the local vercel dev environment, where middleware runs first and redirects are evaluated afterward.

Practical impact

• Any path that appears in both a redirect and middleware will be redirected; the middleware logic will never run for that request.
• Redirects are permanent (308) and are cached by the edge network, so the first hit can be served from cache without hitting your origin.
• Rewrites, in contrast, are evaluated after middleware and allow the request to continue to your application code.

Steps to verify and fix the conflict

1. Deploy a minimal Next.js app with a vercel.json containing:

   {
     "redirects": [
       {
         "source": "/old-path",
         "destination": "/new-path",
         "permanent": true
       }
     ]
   }

2. Add middleware.ts that logs a message and returns a simple response for /old-path.

   import { NextResponse } from 'next/server';
   export function middleware(request) {
     console.log('middleware hit');
     return NextResponse.next();
   }
   

3. Deploy to Vercel and request /old-path from a browser or curl -I https://your-app.vercel.app/old-path.
   • Confirm you receive a 308 redirect to /new-path.
   • Check the Vercel logs – the middleware log should be absent for this request.
4. In the same preview or production environment, request a path that is only in middleware (e.g., /only-middleware) and verify the middleware runs and returns the expected response.
5. If you need the middleware logic to run before a redirect, replace the redirect with a rewrite or move the logic into the destination route.

   {
     "rewrites": [
       {
         "source": "/old-path",
         "destination": "/new-path"
       }
     ]
   }

Assumptions & version context

• Behavior described applies to Vercel’s current stable release (as of 2026‑10) and Next.js 13+ with the Edge Runtime.
• Vercel may adjust the internal order for preview deployments or experimental runtimes; always check the latest docs if you use those features.

Diagnostic question

Do you also use rewrites or headers in your vercel.json? Those rules can affect the exact order of evaluation and might change the outcome for overlapping paths.