Next.js proxy.ts: Redirects, Auth Checks and Rewrites at the Edge of Your App

Sometimes you need to act on a request before any page renders: redirect signed-out users, rewrite a path, or add a header. In Next.js 16 this file is called proxy.ts; earlier versions called it middleware.ts and the idea is the same.

A basic proxy

// proxy.ts (project root, or src/proxy.ts)
import { NextResponse, type NextRequest } from 'next/server';

export function proxy(request: NextRequest) {
  const session = request.cookies.get('session')?.value;

  if (!session && request.nextUrl.pathname.startsWith('/dashboard')) {
    const login = new URL('/login', request.url);
    login.searchParams.set('next', request.nextUrl.pathname);
    return NextResponse.redirect(login);
  }

  return NextResponse.next();
}

export const config = {
  matcher: ['/dashboard/:path*', '/settings/:path*'],
};

Useful patterns

Rewrites serve different content without changing the URL, for example A/B tests or multi-tenant sites:

const host = request.headers.get('host'); // acme.example.com
const tenant = host?.split('.')[0];
return NextResponse.rewrite(new URL(`/tenants/${tenant}${request.nextUrl.pathname}`, request.url));

Response headers:

const res = NextResponse.next();
res.headers.set('X-Frame-Options', 'DENY');
return res;

Rules of thumb

• Keep it fast. It runs on every matching request, so avoid slow database calls.
• Use matcher to skip static files and images.
• A cookie check here is an optimistic redirect for UX, not your security. Still check authorisation in the page, Server Action or API route that reads the data.
• Migrating from middleware.ts? Rename the file and the exported function to proxy; Next.js provides a codemod.