# An introduction to the npm package manager

> An introduction to npm, the standard package manager for Node.js: how to install dependencies, update packages, manage versions, and run scripts.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2018-01-29 | Updated: 2026-07-18 | Topics: [Node.js](https://flaviocopes.com/tags/node/) | Canonical: https://flaviocopes.com/npm/

`npm` is the package manager that comes with [Node.js](https://flaviocopes.com/nodejs/). You use it to install packages, record project dependencies, update them, and run project scripts.

Most npm projects have a `package.json` file and a `package-lock.json` file. Installed packages usually live in the `node_modules` folder.

## Install npm

The simplest way to get npm is to [install Node.js](https://nodejs.org/en/download). npm is included with the official Node.js installers.

You can check the installed versions with:

```bash
node --version
npm --version
```

## Install all project dependencies

If a project has a `package.json` file, run:

```bash
npm install
```

npm reads the dependency lists, installs the packages, and updates `package-lock.json` when needed. The lockfile records the exact dependency tree so repeated installs are more predictable.

In automated environments, use `npm ci` when the project has a lockfile. It performs a clean install and fails if `package.json` and `package-lock.json` disagree.

The [npm install documentation](https://docs.npmjs.com/cli/v11/commands/npm-install/) explains the available install modes.

## Install a package

Install a package your application needs with:

```bash
npm install fastify
```

npm adds it to `dependencies` by default.

Development tools belong in `devDependencies`:

```bash
npm install --save-dev eslint
```

You can also use the shorter `-D` flag:

```bash
npm install -D eslint
```

Use `--save-exact` if you want npm to record one exact version instead of a version range.

## Update packages

Run this to update installed packages within the version ranges allowed by `package.json`:

```bash
npm update
```

You can update one package:

```bash
npm update fastify
```

`npm update` does not normally widen the ranges in `package.json`. The [official `npm update` guide](https://docs.npmjs.com/cli/v11/commands/npm-update/) documents how the command treats package and dependency constraints.

Use this command to see which direct dependencies have newer versions available:

```bash
npm outdated
```

## Package versions

npm packages normally follow **semantic versioning**:

```text
major.minor.patch
```

For version `4.2.1`:

- `4` is the major version
- `2` is the minor version
- `1` is the patch version

A caret range such as `^4.2.1` accepts compatible updates without moving to version 5. A tilde range such as `~4.2.1` stays within version 4.2.

Version zero has stricter caret behavior. For example, `^0.13.0` accepts versions below `0.14.0`, not every `0.x` minor release.

See the [npm semantic versioning guide](https://docs.npmjs.com/about-semantic-versioning/) for the complete range rules.

## Run project scripts

The `scripts` field in `package.json` gives a project short, repeatable commands:

```json
{
  "scripts": {
    "dev": "node --watch server.js",
    "start": "node server.js",
    "test": "node --test"
  }
}
```

Run a script with:

```bash
npm run dev
```

`start` and `test` also have shortcuts:

```bash
npm start
npm test
```

npm adds executables from local dependencies to the script's `PATH`. This means a script can call locally installed tools without a global installation.

The [npm scripts documentation](https://docs.npmjs.com/cli/v11/using-npm/scripts/) describes lifecycle scripts and the environment available to commands.