I’ve been asked how to change the HTTP port of an app built using Next.js, when you are running it locally. By default the port is 3000, but that’s a commonly used port and perhaps you have another service running on it.

How can you change it?

The answer is in the package.json file stored in the Next.js app main folder.

By default the file content is this:

{
  "name": "learn-starter",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "dev": "next dev",
    "build": "next build",
    "start": "next start"
  },
  "dependencies": {
    "next": "9.3.5",
    "react": "16.13.1",
    "react-dom": "16.13.1"
  }
}

Note: the exact package versions will differ in your case, as they get updated

The thing you need to change is the scripts part.

Change:

"dev": "next dev",

to

"dev": "next dev -p 3001"

to start Next.js on port 3001 instead of 3000.

Now when you run npm run dev, the command used to start the development server locally, you will see it start on port 3001:

Lessons in this unit:

0:	Introduction
1:	Absolute imports in Next.js
2:	▶︎ How to change a Next.js app port
3:	Next.js, adding features just to development mode
4:	Next.js: how to show something in development and hide in production
5:	Adding a wrapper component to your Next.js app