What is NPM and How Does it Work?

What is NPM?

NPM (Node Package Manager) is the default package manager for Node.js and the world's largest software registry, with over 2 million packages. It installs and manages your project's dependencies.

Basic Usage

npm init -y              # create package.json
npm install express      # add a dependency
npm install -D jest      # add a dev dependency
npm uninstall express    # remove
npm update               # update packages

package.json — Your Project Manifest

{
  "name": "my-app",
  "version": "1.0.0",
  "scripts": {
    "start": "node index.js",
    "test": "jest"
  },
  "dependencies": {
    "express": "^4.18.0"
  }
}

Running Scripts

npm start
npm test
npm run build   # custom scripts need "run"

FAQs

dependencies vs devDependencies?

Dependencies run in production; devDependencies (test tools, bundlers) are only for development. More in our NPM guides.

What is package-lock.json?

It locks exact versions for reproducible installs — always commit it.