In Next.js 16, middleware.ts was renamed to proxy.ts. The idea is still the same: run code before a request is completed. I usually think of Proxy as a checkpoint between the request and your app:

Request → proxy.ts → Next.js route

What can Proxy do?

Proxy can inspect an incoming request and decide what happens next. For example, you can redirect, rewrite URLs, modify headers, or return a response directly. A simple redirect looks like this:

import { NextResponse } from 'next/server'
import type { NextRequest } from 'next/server'

export function proxy(request: NextRequest) {
  return NextResponse.redirect(
    new URL('/home', request.url)
  )
}

Use matcher when needed

You usually don’t want Proxy to run for every route. Use matcher to limit it:

export const config = {
  matcher: '/admin/:path*',
}

Now Proxy runs for /admin and nested routes, which is useful for things like checking a cookie before accessing an admin area.

Don’t put everything in Proxy

Proxy is better for lightweight request-level logic such as redirects, rewrites, and quick checks. It shouldn’t become your entire authentication or business-logic layer. Keep the heavy work in your server/API layer.

proxy.ts
→ quick request decision

Server / API
→ business logic