How do I install a package as a devDependency instead of a dependency?

Use npm install --save-dev to add a package to devDependencies. A plain npm install, or npm install --save, adds it to dependencies, which is the default behaviour. Choose --save-dev for anything the application does not need once deployed, such as a testing framework or a build tool.

Does npm install install devDependencies too?

Yes. By default npm install installs both dependencies and devDependencies, which is what you want on a development machine. In a production environment run npm install --production instead: that installs only dependencies and skips the development-only packages, keeping the deployed environment leaner.

Why should development tools be kept out of a production deployment?

Leaving development-only tools out of production improves both security and performance. Every package installed on a production server is additional code that has to be trusted and maintained, and testing frameworks, linters and bundlers serve no purpose once the application is built. Installing with npm install --production excludes them automatically.

Which section should a package go in if I am not sure?

Ask whether the running application calls it. If the code imports the package at runtime — a web framework, an HTTP client, a database driver — it belongs in dependencies. If it only runs while you are writing, testing or building the code, it belongs in devDependencies. Getting this right keeps the application working in production and easy to maintain in development.

Understanding Dependencies vs. DevDependencies in Node.js

Q: What is the difference between dependencies and devDependencies in package.json?

Dependencies are the packages an application needs to run in production, such as express, react, axios or mongoose, which the code calls at runtime. DevDependencies are only needed while building the application — jest for tests, eslint for linting, webpack for bundling, babel for transpilation. The split matters because production servers should install only what the running application actually requires.

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TL;DR

When working with Node.js and JavaScript projects using npm or yarn, understanding the difference between dependencies and devDependencies is essential for building efficient, production-ready applications.

In this guide, you'll learn what these terms mean, how they affect your project, and when to use each of them.

If you're starting with Node.js or working on your first JavaScript project, you’ve probably seen two sections in your package.json file: dependencies and devDependencies.

At first glance, they seem similar—but they serve very different purposes. Understanding the difference is important so your project runs smoothly in development and production.

What Are Dependencies?

dependencies are the packages your project needs to run in production. These are essential libraries that your application directly uses during runtime.

Examples:

express – for building APIs and servers
react – for user interfaces
axios – for HTTP requests
mongoose – for MongoDB operations

Where They Appear:

They are listed in your package.json like this:

"dependencies": { "express": "^4.18.2", "axios": "^1.4.0" }

When to Use:

Add a package to dependencies when your application requires it to function during runtime or in a live production environment.

What Are DevDependencies?

devDependencies are the packages your project needs only during development. These help with testing, code quality, building, and development tools.

Examples:

jest – for writing tests
eslint – for linting code
webpack – for bundling assets
babel – for JavaScript transpilation

Where They Appear: They are listed like this in package.json:

"devDependencies": { "jest": "^29.6.0", "eslint": "^8.37.0" }

When to Use:

Use devDependencies for packages that are not required once the application is deployed, such as testing frameworks or build tools.

Installation Tip By default, running npm install installs both dependencies and devDependencies.

However, for production environments, use:

npm install --production

This installs only dependencies, excluding development-only packages to keep your production environment lean.

Comparison Table

Feature	dependencies	devDependencies
Required in production	Yes	No
Used during runtime	Yes	No
Used for development	No	Yes
Installed with --production	Yes	No
Example packages	react, axios	jest, eslint

Best Practices

Use npm install or npm install --save to add to dependencies (default behavior).
Use npm install --save-dev to add to devDependencies.
Keep your package.json clean and well-maintained.
Avoid including unnecessary dev tools in your production deployment to improve security and performance.

Conclusion

The distinction between dependencies and devDependencies in Node.js plays a crucial role in managing your application efficiently. Using the correct type ensures your application works smoothly in production while remaining easy to develop and maintain.