Unlocking the Power of Yarn PnP: Faster, Cleaner, More Secure Dependency Management

What is Yarn Plug’n’Play (PnP)?

Yarn Plug’n’Play (PnP) is an alternative module resolution strategy introduced in Yarn v2 to improve dependency management. Unlike the traditional node_modules structure, PnP eliminates the need for installing dependencies in a node_modules folder and instead directly references them from a global cache.

This approach enhances performance, reduces disk usage, and improves package resolution reliability.

Why Was Yarn PnP Introduced?

In traditional node_modules dependency management:

• Every package installs its own dependencies, leading to duplicate copies.
• The node_modules folder grows excessively large.
• File resolution is slower due to deep folder structures.
• Dependency mismatches can occur due to incorrect package resolutions.

Yarn PnP was introduced to solve these issues by removing node_modules and mapping dependencies efficiently.

How Does Yarn PnP Work?

1. No More node_modules

Instead of downloading and placing dependencies in a node_modules directory, Yarn stores all dependencies in a single global cache and creates a virtual file system (VFS).

2. Faster Dependency Resolution

Dependencies are referenced through a single .pnp.cjs file, which acts as a dependency map. This avoids slow recursive lookups in node_modules.

3. Enhanced Security & Stability

Since dependencies are only accessible through the PnP runtime, packages cannot modify files in node_modules, preventing unexpected issues.

4. Better Disk Space Utilization

Dependencies are deduplicated and shared across projects, reducing disk space usage significantly.

Benefits of Yarn PnP

FeatureTraditional node_modulesYarn PnPDependency ResolutionSlow (recursive file system lookups)Fast (direct mapping)Disk UsageLarge (node_modules takes up space)Small (global cache)Installation SpeedSlower (each package installs dependencies)Faster (dependencies resolved from cache)SecurityPackages can modify filesStrict isolation prevents tamperingDebuggingHarder to track dependency issuesEasier with .pnp.cjs mapping

How to Use Yarn PnP?

1. Enable PnP in Your Project

If you’re using Yarn v2 or later, you can enable PnP by running:

yarn set version berry
yarn config set nodeLinker pnp

This sets up PnP in your project.

2. Install Dependencies

Once PnP is enabled, install dependencies as usual:

yarn install

This creates a .pnp.cjs file instead of a node_modules folder.

3. Running a Script

Run your Node.js application normally:

yarn run <script-name>

Since node_modules no longer exists, Yarn automatically resolves dependencies from .pnp.cjs.

Characteristics of Yarn PnP

1. Dependency Isolation → Dependencies are not installed globally but referenced from a central store.
2. Faster Installs → Avoids filesystem lookups and resolves packages instantly.
3. Lightweight Projects → No node_modules → smaller repositories.
4. Works with Most JavaScript Projects → Compatible with Webpack, TypeScript, Babel, etc.
5. Better Debugging → Dependency tree is clearly defined in .pnp.cjs.

Example: Using Yarn PnP in a React Project

Step 1: Initialize a React Project with Yarn PnP

yarn create react-app my-app --use-pnp
cd my-app

Step 2: Install Dependencies

yarn add axios

Step 3: Running the App

yarn start

Since node_modules doesn’t exist, dependencies are fetched directly from Yarn’s global cache.

Example:Step-by-Step Setup with Yarn and PnP

1. Install Yarn 2+

To get started, you’ll need Yarn 2+ (Berry). You can install it globally by running:

npm install -g yarn

Alternatively, you can follow the official Yarn installation guide to ensure you’re using Yarn 2+ (Berry).

2. Initialize a New Yarn Project

Once Yarn is installed, navigate to your project folder and initialize a new Yarn project:

mkdir my-project
cd my-project
yarn init -2

This will initialize a new project with Yarn 2+ and generate the necessary configuration files, including a .yarnrc.yml file.

3. Enable PnP

By default, Yarn 2+ uses Plug’n’Play (PnP). To ensure that PnP is enabled, check your .yarnrc.yml file for the following setting:

nodeLinker: pnp

If it’s not present, you can manually add it to enable PnP. This tells Yarn to use the PnP package resolution method rather than the default node_modules folder.

4. Install Dependencies

Now, you can install any necessary dependencies for your project, as you normally would with Yarn:

yarn add express

Yarn will resolve and install dependencies without creating a node_modules folder. Instead, it uses the .pnp.cjs file for managing dependency paths.

5. Using the .pnp.js or .pnp.cjs File

The .pnp.js (or .pnp.cjs) file is automatically generated by Yarn and contains mappings to your installed dependencies. This file handles package resolution, and you do not need a node_modules folder anymore.

6. Configuring Node.js for PnP

To ensure that Node.js works with Yarn’s PnP system, you’ll need to add the following line to your entry JavaScript file (e.g., index.js):

require('./.pnp.cjs'); // Or require('./.pnp.js') depending on your setup

This line makes sure that the Node.js runtime respects the package resolution logic provided by Yarn PnP.

7. Troubleshooting

If you encounter any issues with missing modules or packages, ensure the following:

• Dependencies: Verify that all dependencies are properly installed. You can run yarn install again to ensure they are all resolved correctly.
• Module Resolution: Ensure that modules are resolved via Yarn’s PnP loader, which is enabled by the .pnp.cjs (or .pnp.js) file.

If you continue to encounter issues, check if the required package is listed in your package.json and whether there are any conflicts or missing dependencies.

By following these steps, you’ll have a PnP-enabled Node.js project with Yarn 2+, which can improve performance and eliminate the need for a node_modules folder. Yarn’s PnP system is designed to speed up installs and make your dependency management more reliable and predictable.

Potential Issues & Workarounds

IssueSolutionSome libraries expect node_modulesUse nodeLinker: node-modules as a fallbackTools like ESLint may not workUse yarn dlx eslint instead of npxIDEs may not recognize dependenciesInstall the Yarn PnP plugin for VSCode.

Conclusion

Yarn Plug’n’Play (PnP) significantly improves package management by eliminating node_modules, speeding up resolution, and improving security. While some tools need adjustments to work with PnP, the performance gains and disk space savings make it a valuable feature for modern JavaScript projects.

If you’re building a large-scale application, consider using Yarn PnP for faster, leaner, and more secure dependency management.