npm, Yarn, pnpm and Bun: Package Managers Explained Simply

When you build JavaScript projects today, you do not just write code. You also choose who manages your packages, builds your app and keeps everything consistent. For years, npm ruled this space without competition. Then Yarn challenged it. Then pnpm arrived with a smarter design. Now Bun is trying to rebuild the entire experience from the ground up.

If you ever felt confused about which one to use, you are not alone. Let me break them down with explanations, examples and a bit of context so the whole picture becomes clear.

Understanding the four players

npm: The default that everyone knows

npm ships with Node.js and controls the largest package registry in the JavaScript ecosystem.

To install a package:

npm install axios

To run a script:

npm run build

It works everywhere and every library expects it to work.

The biggest advantage of npm is simplicity and universal compatibility. The biggest downside used to be speed and inconsistent installs. npm has improved a lot in recent years, but there are still faster alternatives.

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Yarn: The first serious challenger

Yarn was created by Facebook because npm had performance issues at the time. Yarn improved reliability with lockfiles, added workspaces and introduced an optional feature called Plug and Play.

Example: Yarn install

yarn add axios

Example: Yarn workspaces (package.json)

{
  "private": true,
  "workspaces": [
    "packages/api",
    "packages/web"
  ]
}

Workspaces made monorepos easy to manage.

Yarn Plug and Play

Plug and Play removes node_modules and replaces it with a virtual resolution system. It can speed up installs and reduce clutter, but some tools still expect node_modules.

If you want customisable tooling and powerful monorepo support, Yarn is great.

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pnpm: The clever and strict one

pnpm is gaining massive popularity because it saves disk space and enforces strict dependency rules. It uses a content-addressed storage system that keeps one copy of each package on your machine. All projects link to that single store.

This is how it installs packages:

pnpm add axios

Why pnpm saves space

If you have 20 projects using React, npm and Yarn will store React 20 times.

pnpm stores React once and creates links to it.

Why pnpm prevents hidden bugs

Traditional node_modules flattening sometimes lets you import packages you never installed directly.

Example of a mistake:

import lodash from "lodash"

If you did not install lodash but another package depended on it, npm or Yarn may still allow this. pnpm will not. It makes every dependency explicit.

Example: pnpm workspace setup

packages:
  - "apps/*"
  - "packages/*"

This is one of the reasons many teams love pnpm when working with monorepos.

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Bun: The new kid that is rebuilding everything

Bun is not just a package manager. It is a runtime, bundler, test runner and a toolchain all packed into one binary. It is written in a language called Zig, which focuses on speed and low level control. If you want to learn what Zig is, here is the official site:

https://ziglang.org/

Bun uses JavaScriptCore, the same engine used in Safari. It starts faster than Node.js in many cases.

Bun install

bun install

This alone is incredibly fast.

Bun runtime example

bun run index.ts

Bun HTTP example

export default {
  port: 3000,
  fetch(req) {
    return new Response("Hello from Bun")
  }
}

And run it with:

bun server.js

Bun feels refreshing because it tries to simplify the entire developer experience.

The main drawback is that Bun is still very young. Some Node APIs and native modules may not behave exactly the same. But it is improving fast.

A real world comparison

Feature	npm	Yarn	pnpm	Bun
Speed	Slow to moderate	Fast	Very fast	Extremely fast
Disk usage	High	High	Very low	Low
Monorepo support	Basic	Great	Excellent	Basic
node_modules	Yes	Optional	Smart node_modules	Yes but optimized
Runtime	No	No	No	Yes
Bundler	No	No	No	Yes

Which one should you choose?

Here is the simple version.

• Choose npm if you want maximum compatibility.
• Choose Yarn if you want strong workspaces and extra tooling.
• Choose pnpm if you want speed, strict dependency isolation and a monorepo that feels clean.
• Choose Bun if you want a fast runtime and an all in one toolset that simplifies the entire development flow.

There is no single winner. Your choice depends on how you like to build and what you value more: stability, features, structure or raw speed.