What is the difference between “npm install” and “npm ci”?

When working with Node.js projects, understanding the commands provided by npm (Node Package Manager) is crucial. Two commonly used commands are npm install and npm ci. While they might seem similar at a glance, they serve distinct purposes and behave differently depending on the context. Let’s delve into the differences between them and when to use each.

What is npm install?

npm install is the most frequently used command in npm. It installs the dependencies listed in your package.json file. Here’s what happens when you run this command:

1. 1. Dependency Installation:
      • npm install checks the package.json file for dependencies and installs them into the node_modules directory.
      • If a package-lock.json file exists, npm tries to match the exact versions specified there.
      • If there is no package-lock.json, npm generates one during the installation process.
   2. Behavior with Missing Dependencies:
      • If you add a new dependency to your package.json file and run npm install, npm installs the new dependency and updates the package-lock.json file accordingly.
   3. Flexibility:
      • It is tolerant of minor discrepancies between package.json and package-lock.json.
      • For example, it allows for updates to sub-dependencies within the range specified by semver (semantic versioning).
   4. Use Case:
      • Use npm install during development when you need to add or update dependencies.

What is npm ci?

npm ci stands for “Continuous Integration.” It is designed for environments where consistency and speed are critical. Here’s how it works:

1. Strict Lockfile Adherence:
   • Unlike npm install, npm ci relies exclusively on the package-lock.json file.
   • If the package-lock.json file is missing or doesn’t match the package.json file, the command will fail.
2. Clean Installation:
   • Before installing, npm ci deletes the existing node_modules directory entirely.
   • It ensures a fresh, clean slate by installing dependencies exactly as specified in the package-lock.json file.
3. Faster Execution:
   • Since npm ci skips steps like generating a new package-lock.json file and recalculating dependencies, it’s faster than npm install.
4. Use Case:
   • Use npm ci in CI/CD pipelines where you need a predictable and reproducible environment.
   • Ideal for automated testing or production builds.

Key Differences Between npm install and npm ci

When to Use Each Command

1. npm install********:
   • During development to add or update dependencies.
   • When you don’t have strict requirements for a clean installation.
2. npm ci********:
   • In CI/CD pipelines for consistent builds.
   • When you want to ensure a predictable, reproducible environment.

Both npm install and npm ci are essential tools for Node.js developers, each serving unique purposes. Understanding their differences can help you choose the right command for your use case. Use npm install during active development and npm ci for production and testing environments where consistency is paramount.