nested-middleware.md

Nested Middleware Deprecated

Why This Error Occurred

You are defining a middleware file in a location different from pages/_middleware which is deprecated.

Declaring a middleware file under specific pages implied that it would only be executed when pages below its declaration were matched. This execution model allowed the nesting of multiple middleware, which is hard to reason about and led to consequences such as dragging effects between different middleware executions.

The API has been deprecated in favor of a simpler model with a single root middleware.

Possible Ways to Fix It

To fix this error, declare your middleware in the root pages folder and use NextRequest parsed URL to define which path the middleware code should be executed for. For example, a middleware declared under pages/about/_middleware.js can be moved to pages/_middleware. A conditional can be used to ensure the middleware executes only when it matches the about/* path:

import type { NextRequest } from 'next/server'

export function middleware(request: NextRequest) {
  if (request.nextUrl.pathname.startsWith('/about')) {
    // Execute pages/about/_middleware.js
  }
}

If you have more than one middleware, you will need to combine them into a single file and model their execution depending on the request.