Yarn and npm are two of the most popular package managers used in the JavaScript ecosystem to manage project dependencies. Both tools enable developers to easily install, update, and manage the libraries and packages their projects rely on. While npm is the default package manager for Node.js, Yarn was created by Facebook as an alternative with performance improvements and a more deterministic dependency management system.

In this article, we'll explore what Yarn and npm are, their key differences, and when to use each tool.

What Is npm?

npm (Node Package Manager) is the default package manager bundled with Node.js. It allows developers to easily install and manage third-party libraries or packages that are needed for their JavaScript projects. npm has become an essential tool for both backend (Node.js) and frontend (React, Angular, Vue) development.

npm provides the following functionalities:

• Package installation: Install packages (also known as dependencies) from the npm registry using simple commands.
• Version management: Specify exact or compatible versions of packages that your project depends on.
• Dependency tree management: Automatically manage sub-dependencies required by your project's main dependencies.

Example of Installing a Package with npm

To install a package like lodash using npm, you can run:

This will download the package from the npm registry and add it to your project’s node_modules folder.

What Is Yarn?

Yarn is a JavaScript package manager created by Facebook in 2016 to address some of the performance and security issues present in npm at the time. While Yarn shares many of the same features as npm, it introduced improvements like faster dependency resolution and more reliable lockfiles that ensure deterministic builds.

Yarn focuses on:

• Speed: Yarn is often faster than npm because of its efficient caching and parallelization of tasks.
• Deterministic installs: Yarn uses a lockfile (yarn.lock) to ensure that dependencies are resolved in a consistent and predictable manner across different environments.
• Offline support: Yarn caches every package it downloads, so you can install packages without an internet connection if they were previously installed.

Example of Installing a Package with Yarn

To install the same lodash package using Yarn, you can run:

This command performs a similar task to npm’s install, but uses Yarn’s features like caching and lockfile management.

Key Differences Between Yarn and npm

1. Performance

npm:

npm installs dependencies sequentially, which can sometimes make it slower, especially for projects with a large number of dependencies.

Yarn:

Yarn optimizes performance by installing dependencies in parallel and caching packages, making subsequent installs faster. This is particularly useful for large projects and monorepos.

2. Lockfiles

npm:

npm generates a package-lock.json file to ensure that the exact versions of dependencies are installed. This helps in maintaining consistency across different environments.

Yarn:

Yarn generates a yarn.lock file, which is more deterministic. It guarantees that the same dependency versions are installed every time, avoiding potential issues related to version mismatches.

3. Offline Support

npm:

npm has limited offline capabilities. If you’ve installed a package before, it may be cached, but this behavior is not guaranteed.

Yarn:

Yarn excels in offline support. It caches every package it downloads, so you can use it even without an internet connection as long as the required package was previously installed.

4. Workspaces

npm:

npm introduced workspaces in version 7, allowing you to manage multiple packages in a monorepo setup. However, this feature is still relatively new and lacks some of the maturity of Yarn’s implementation.

Yarn:

Yarn’s workspaces feature has been around for longer and is more robust. It simplifies managing monorepos, where multiple related packages are stored in a single repository.

5. Security

npm:

npm provides basic security features, such as warning developers about known vulnerabilities when installing packages.

Yarn:

Yarn performs integrity checks by verifying that the package contents match the hash stored in the lockfile. This additional security layer helps prevent tampering with packages.

When to Use npm

• Default setup: If you’re working with Node.js, npm comes bundled, making it the simplest and most convenient option for many projects.
• Broad ecosystem: npm is widely supported and has the largest package registry, so it’s ideal for projects that don’t need specialized features like Yarn’s caching or workspaces.
• New features in npm 7+: With recent updates, npm has introduced workspaces and improved performance, making it a competitive option for managing monorepos and speeding up dependency installations.

When to Use Yarn

• Speed and efficiency: If your project requires faster dependency installs and better performance, Yarn is often the better choice due to its caching and parallel processing.
• Monorepo support: For projects using a monorepo architecture, Yarn’s workspaces are more mature and better suited for managing multiple packages within a single repository.
• Offline installs: If you need to install dependencies without an internet connection, Yarn’s built-in offline mode can be a significant advantage.