Yarn Package Manager - npm's Faster Cousin

Back in 2016, npm was a shitshow.

Slow installs, inconsistent dependency resolution, and zero-installs that somehow took 10 minutes. Facebook got fed up and built Yarn to fix what npm couldn't handle.

What Actually Changed

npm 11.6.0 (released September 2025) is pretty decent now, but Yarn still has advantages:

Yarn's lockfile is bulletproof. Your yarn.lock guarantees the same dependency tree every time. npm's package-lock.json gets corrupted more often than you'd like.

Workspaces that don't suck. If you're doing monorepos, Yarn workspaces actually work. npm workspaces exist but feel like an afterthought.

Better caching. Once Yarn downloads a package, it's cached globally.

No more downloading React 47 times for different projects.

The PnP Problem

Here's where things get complicated. Yarn's Plug'n'Play mode generates a `.pnp.cjs` file instead of node_modules.

Sounds great

• no more dependency hell!

Reality check: PnP breaks half your tools. ESLint extensions stop working in VS Code. Some packages just refuse to load.

I've seen teams spend weeks debugging PnP compatibility issues.

The good news? Yarn 4.9.4 defaults to node_modules mode now.

You can enable PnP if you hate yourself.

Performance Reality Check

Benchmark data shows cached installs are fast:

• Yarn: ~1-2 seconds for most projects
• npm: ~3-5 seconds
• pnpm:

Usually fastest at ~0.5-1 seconds

But first installs? Expect 30-60 seconds regardless of your package manager. The network is still the bottleneck.

When Yarn Makes Sense

Use Yarn if:

• You're building monorepos (workspaces are genuinely good)
• Your team keeps getting different dependency versions
• npm installs keep failing mysteriously

Stick with npm if:

• Your project is simple
• You don't want to learn new commands
• Your CI/CD is already set up

Try pnpm if:

• You want the fastest installs
• Disk space matters (shared dependencies across projects)

PnP Mode: Great Idea, Painful Reality

Yarn's Plug'n'Play mode sounds amazing on paper. No more node_modules! Faster installs! Perfect dependency resolution!

What actually happens:

Your ESLint VS Code extension breaks. Your test runner can't find modules. Half your build tools throw cryptic errors like:

Error: @babel/preset-env tried to access @babel/core (a peer dependency) 
but it isn't provided by its ancestors

Great error message, but good luck explaining to your junior dev why the build randomly broke.

I spent 3 days debugging a TypeScript project where PnP couldn't resolve type definitions. The solution? Disable PnP and go back to node_modules.

The smart move: Yarn 4.9.4 defaults to nodeLinker: node-modules now. Use that unless you enjoy pain.

Workspaces: Actually Good

This is where Yarn shines. Yarn workspaces for monorepos are genuinely well-designed.

yarn workspace @mycompany/api add express
yarn workspaces run build
yarn workspaces run test --parallel

It just works. npm workspaces feel like they were added because Yarn had them. Yarn's implementation is thoughtful.

Real example: I migrated a 12-package monorepo from Lerna + npm to Yarn workspaces. Build times dropped from 8 minutes to 3 minutes, and dependency management became sane.

Security Theater vs Reality

Yarn's security features sound impressive:

• Lockfile checksums prevent tampering
• Ghost dependency protection catches missing deps
• Reproducible builds across environments

In practice: The same npm supply chain attacks that hit npm packages also hit Yarn. The September 2025 chalk/debug attack affected both package managers equally.

The ghost dependency protection is legitimately useful though. It catches the "works on my machine" bugs where you accidentally rely on a transitive dependency.

Performance: Good, Not Magic

Yarn is faster than npm, especially for cached installs. But it's not magic:

Cold installs: Still slow. Network and CPU bound.
Warm installs: Fast, but pnpm is faster.
Workspace installs: Genuinely faster than alternatives.

Windows pain point: Yarn installs randomly fail with `EPERM` errors on Windows. Usually fixed by running as administrator or disabling antivirus, but it's frustrating.

Migration Reality Check

Migrating from npm to Yarn takes longer than you think:

1. Install Yarn: `npm install -g yarn` (ironic, I know)
2. Remove node_modules: `rm -rf node_modules package-lock.json`
3. Run: `yarn install`
4. Fix broken scripts: Your npm scripts might need tweaking
5. Update CI/CD: Change all your build pipelines
6. Fight with Docker: Your Dockerfile needs updates
7. Debug weird issues: Something will break randomly

Budget 1-2 days for a proper migration, not the "5 minutes" the docs suggest.