How to Use package.json for Node.js Projects
Updated: February 2026
The package.json file is the manifest for Node.js projects, containing metadata, dependencies, scripts, and configuration. Every Node.js project should have package.json for dependency management and project information.
Opening package.json
JSON format text file. Open with any text editor. VS Code provides JSON validation and IntelliSense for package.json.
Basic Structure
{
"name": "my-project",
"version": "1.0.0",
"dependencies": {
"express": "^4.18.0",
"lodash": "~4.17.0"
},
"scripts": {
"start": "node app.js"
}
}
Installing Dependencies
Run
npm install
to install all packages listed in dependencies. Creates
node_modules
folder with all packages.
npm install express
- Install package and add to package.json
npm install --save-dev jest
- Add development dependency
Version Ranges
^4.18.0
- Compatible with 4.x.x (allows minor updates)
~4.17.0
- Compatible with 4.17.x (patch updates only)
4.18.0
- Exact version
Creating package.json
Run
npm init
to create interactively, or
npm init -y
for defaults. Customize fields as needed.
Scripts
Define custom commands in "scripts" section. Run with
npm run scriptname
or
npm start
for start script.
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