npm i vs npm ci: What’s the Difference, and When Should You Use Them?

If you’ve been working with Node.js projects, you’ve probably typed npm i more times than you can count. But have you ever wondered what makes npm ci different from your trusty npm install? Is one faster? Safer? Or just… redundant? Let’s dive in and break it down.

📋 Quick Summary (short answer)

Use npm install for flexibility during development.
Use npm ci for speed and reliability in clean builds or deployments.

Both commands have their place in your toolkit, choose the one that fits the task.

🚀 Why This Matters

Imagine you’re about to deploy a project. You run npm install, and boom—something breaks. Maybe the wrong dependency version sneaked in, or your node_modules folder looks slightly… cursed. That’s where understanding these two commands can save your day (and your sanity).

🤔 The Basics: What Do These Commands Do?

npm install (or npm i)

npm install is the go-to command for downloading dependencies. It does the following:

Reads your package.json file.
Resolves versions of the dependencies listed there.
Downloads and installs them into a node_modules folder.

If you’ve already run npm install before, it’ll also check your package-lock.json (if available) and try to follow the versions listed there.

Key Features:

Flexible: Automatically updates your package-lock.json if new versions are available.
Handy for development: Works well during the early stages of a project, where dependencies might change often.

npm ci

The ci in npm ci stands for Continuous Integration, but it’s not just for CI/CD pipelines. This command ensures exactly reproducible builds. Here’s what it does:

Reads your package-lock.json (not just package.json).
Completely removes node_modules and installs dependencies exactly as listed in package-lock.json.

Key Features:

Strict: Fails if your package-lock.json is missing or out of sync with package.json.
Fast: Skips dependency resolution and installs directly from package-lock.json.
Ideal for CI/CD: Guarantees identical setups across different environments.

🕵️‍♂️ Key Differences: npm i vs npm ci

Feature	npm install	npm ci
Dependency Resolution	Resolves versions and updates `package-lock.json` as needed.	Installs exact versions from `package-lock.json`.
Speed	Slower due to version resolution.	Faster because it skips resolution.
Use Case	Great for local development.	Perfect for CI/CD and deployments.
Strictness	Flexible with missing/outdated `package-lock.json`.	Requires a valid and synced `package-lock.json`.
Node_Modules Cleanup	Doesn’t remove `node_modules`.	Removes and rebuilds `node_modules`.

🛠️ When Should You Use Each?

Use `npm install` when:

You’re actively developing and might add/remove dependencies.
You need to update your package-lock.json to reflect changes.

Use `npm ci` when:

You’re working in a clean environment (e.g., a CI/CD pipeline or Docker build).
Reproducibility is critical—like production builds.
You want to ensure the environment matches your package-lock.json exactly.

✨ Fun Facts & Tips

Why “ci”?
It’s short for Continuous Integration, but it’s perfectly fine to use it outside CI/CD (anytime you need consistent installs).
npm ci is faster!
By skipping dependency resolution, npm ci is often 2-3x faster than npm install.
Got an outdated lock file?
Run npm install first to sync your package-lock.json, then use npm ci for subsequent builds.
Error-Prone Areas:
If your package-lock.json is out of sync with package.json, npm ci will fail. Keep those files updated!

💡 Ready to Try It?

Next time you’re setting up a project, think about the environment. Need speed and consistency? Go with npm ci. Want flexibility? Stick with npm install.

Got any other npm curiosities? Drop your questions below, or share this post with a fellow dev who’s still figuring out their npm game! 🚀