Next.js provides the flexibility to change the default port of the development server using command-line options such as -p <port_number> or by updating the “scripts” section in the package.json file, offering developers multiple ways to customize the port configuration based on their requirements.

Steps to Create the Next App

Step 1: Set up Next.js Project using the Command:

npx create-next-app port-change

Step 2: Navigate to the Project folder using:

cd port-change

Project Structure:

The updated dependencies in package.json file will look like:

  "dependencies": {
    "react": "^18",
    "react-dom": "^18",
    "next": "14.2.1"
  }

Approach 1: Updating package.json File

In this approach, we are updating the “scripts” section in package.json to specify the desired port, such as “dev”: “next dev -p 3001“. This configures Next.js to run on the specified port when using the development script, allowing the React component to detect and display the current port when a button is clicked.

Syntax:

 "dev": "next dev -p "port_Number", 

Update the “scripts” section in package.json to specify the desired port:

{
 "scripts": {
   "dev": "next dev -p 3001", 
   "build": "next build",
   "start": "next start"
 }
}

Example: The below example is displayed on the port number which is updated in package.json file.

//src/app/page.js
'use client';
import React from 'react';

const Page = () => {
  const handleButtonClick = () => {
    const currentPort = window.location.port || 3000; // Default port if not specified
    alert(`The current port is: ${currentPort}`);
  };

  return (
    <div>
      <h1>Approach 1: Updating package.json File</h1>
      <button onClick={handleButtonClick}>Show Current Port</button>
    </div>
  );
};

export default Page;

Step to run the application: Now run the application with the below command:

npm run dev

Output:

Approach 2: Specify Port Number in Run Command

In this approach, we specify the port number when running the Next.js development server using the command npm run dev — -p <port_number>, allowing the React component to detect and display the current port when a button is clicked without altering the package.json file.

Syntax:

npm run dev -- -p <port_number>

Example: The below example is displayed on the port number which is specified in the run command.

'use client';
import React from 'react';

const Page = () => {
  const handleButtonClick = () => {
    const currentPort = window.location.port || 3000; 
    alert(`The current port is: ${currentPort}`);
  };

  return (
    <div>
      <h1>Approach 2: Specify Port Number in Run Command</h1>
      <button onClick={handleButtonClick}>Show Current Port</button>
    </div>
  );
};

export default Page;

Step to run the application: Now run the application with the below command:

npm run dev -- -p 3005

Output: