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Filtering query parameters

Learn how to filter query parameters in your Middleware.

DX Team
Knowledge Base
1 min read
Last updated November 11, 2025

The following example shows how to filter query parameters in your Middleware.

Your middleware file should be placed at the root of your project. If you are using the src directory, the file should be placed in the src directory.

middleware.js
import { NextResponse } from 'next/server';


const allowedParams = ['allowed'];


export const config = {
  matcher: '/',
};


export default function middleware(request) {
  const url = request.nextUrl;
  let changed = false;


  url.searchParams.forEach((_, key) => {
    if (!allowedParams.includes(key)) {
      url.searchParams.delete(key);
      changed = true;
    }
  });


  // Avoid infinite loop by only redirecting if the query
  // params were changed
  if (changed) {
    return NextResponse.rewrite(url);
  }
}
middleware.ts
import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';


const allowedParams = ['allowed'];


export const config = {
  matcher: '/',
};


export default function middleware(request: NextRequest) {
  const url = request.nextUrl;
  let changed = false;


  url.searchParams.forEach((_, key) => {
    if (!allowedParams.includes(key)) {
      url.searchParams.delete(key);
      changed = true;
    }
  });


  // Avoid infinite loop by only redirecting if the query
  // params were changed
  if (changed) {
    return NextResponse.rewrite(url);
  }
}

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