Understanding the Difference Between `npm install` and `npm ci`

Overview

As Node.js applications grow, dependency management becomes crucial for ensuring reliable, consistent builds. npm install and npm ci are two commands available in npm to handle dependencies, each with a specific purpose and optimal context. Understanding the differences between them is key to improving build consistency and speed, particularly in CI/CD pipelines.

In this post, we’ll break down the differences between npm install and npm ci, when to use each, and how to implement them effectively.

Key Differences Between npm install and npm ci

At a high level, npm install and npm ci both install dependencies, but they do so in distinct ways that suit different workflows:

Let’s dig deeper into each command and the scenarios where they’re most useful.

1. npm install: Flexible for Development

npm install is the command most Node.js developers are familiar with. It installs all dependencies listed in package.json and will create or update the package-lock.json file to reflect the installed versions.

Key Characteristics of npm install

• Primary Use: Best suited for development environments where dependencies may change or be added.
• Creates or Updates package-lock.json: If a package-lock.json file exists, npm install will use it as a reference for exact version numbers, but it can still update the lock file if there’s a discrepancy with package.json (e.g., a new package or updated version).
• Network Requests: npm install may download new packages or versions as necessary, which can slow down the installation process if your dependencies aren’t already cached.

When to Use npm install

Use npm install in development contexts where:

• You’re actively adding or updating dependencies.
• Flexibility in dependency versions is acceptable.
• You’re okay with updates in package-lock.json as new dependencies are introduced.

Example

npm install

This command will install dependencies from package.json and make updates to package-lock.json as necessary.

2. npm ci: Ideal for Reproducible Builds

npm ci stands for “clean install” and is designed for use in continuous integration (CI) and production environments. It’s intended for situations where reproducibility, speed, and reliability are prioritized over flexibility.

Key Characteristics of npm ci

• Requires Both package.json and package-lock.json: npm ci relies on the exact versions specified in package-lock.json and will fail if package-lock.json and package.json are out of sync.
• Strict Version Matching: Ensures all dependencies match the exact versions listed in package-lock.json, providing a consistent environment across different machines and environments.
• Faster Installation: Skips the dependency resolution process, as all versions are already locked in the lock file, making npm ci faster than npm install.

When to Use npm ci

Use npm ci in CI/CD and production environments when:

• You want to ensure reproducible builds with exact dependency versions.
• You need a fast, reliable installation process without updating the lock file.
• Consistency across multiple deployments is critical.

Example

npm ci

This command installs dependencies strictly as specified in package-lock.json. It will throw an error if package-lock.json and package.json are not in sync.

Pros and Cons: npm install vs npm ci

npm install

Pros:

• Flexible: Allows for updates to dependencies, making it suitable for development.
• Automatically updates package-lock.json to reflect changes in package.json.

Cons:

• Slower than npm ci as it may need to resolve dependencies and make network requests.
• Can lead to inconsistent dependency versions in CI environments if the lock file is modified during installation.

npm ci

Pros:

• Fast and reliable: Ideal for reproducible builds in CI/CD pipelines.
• Ensures exact versions match those in package-lock.json.

Cons:

• Rigid: Will fail if there’s a mismatch between package-lock.json and package.json.
• Less suitable for active development where dependencies frequently change.

Example Workflow: Development vs. Production

To optimize your workflows, use npm install in development and npm ci in production or CI pipelines. Here’s a simple breakdown:

1. Development:

   • Use npm install to add or update dependencies.
   • Commit changes to package-lock.json if new packages are added.

2. CI/CD or Production:

   • Use npm ci to ensure fast, consistent builds with exact versions from package-lock.json.

Conclusion

Both npm install and npm ci play important roles in modern JavaScript development. Use npm install in development for flexibility and npm ci in CI/CD for predictable, reliable builds. By leveraging each command in its optimal environment, you can streamline your build processes, reduce unexpected errors, and ensure consistent application behavior across different environments.

Happy coding!