Monorepos with Bun

📦 Monorepos with Bun: A Modern Setup Guide

Managing large-scale JavaScript applications across multiple packages can be messy. That’s where Monorepos come in — allowing you to organize multiple related packages in a single codebase. With the rise of Bun, setting up and working with monorepos has become faster, simpler, and more efficient. In this guide, we’ll explore how to build and manage Monorepos with Bun step-by-step.

🧱 What is a Monorepo?

A monorepo (monolithic repository) is a development strategy where all your packages, libraries, and applications live in a single repository. This approach improves dependency sharing, version control, and collaborative development across teams.

Common use cases:

• Managing frontend and backend in one repo
• Maintaining shared libraries across apps
• Modular microservices development

⚡ Why Bun for Monorepos?

Bun has native support for workspaces, making monorepo management incredibly smooth. Unlike other tools where you need third-party configurations (like Lerna or Turborepo), Bun handles it internally via its configuration system.

Key advantages:

• Ultra-fast installs and linking
• Zero-config workspace support
• Built-in tooling (bundler, test runner, transpiler)

🛠️ Setting Up a Bun Monorepo

Let’s walk through setting up a monorepo using Bun’s built-in workspace support.

📁 Project Structure Example

my-monorepo/
├── bunfig.toml
├── packages/
│   ├── app/
│   │   └── package.json
│   └── utils/
│       └── package.json

The packages folder contains all your sub-packages. Each one is a self-contained npm package.

🔧 Configuring bunfig.toml

To enable workspace support, define the following in your bunfig.toml file:

[workspace]
packages = ["packages/*"]

This tells Bun to treat every folder inside packages/ as a separate package and automatically link them when running bun install.

📦 Installing Dependencies

Run the install command once from the root folder:

bun install

Bun will resolve all dependencies and link the internal packages together — no need for manual symlinks or extra setup.

🔗 Linking Local Packages

If your app depends on utils, just add it as a dependency like this:

// packages/app/package.json
{
  "name": "app",
  "dependencies": {
    "utils": "*"
  }
}

Bun understands the monorepo structure and automatically links the local utils package.

🚀 Running Code Within Packages

Each workspace package can be independently developed and executed. For example:

cd packages/app
bun run start

This keeps your development modular and focused, while still benefiting from shared code and dependencies.

🧪 Built-in Testing with Bun

Bun has a built-in test runner that works seamlessly inside monorepos. Example:

// packages/utils/math.test.ts
import { expect, test } from "bun:test";
import { add } from "./math";

test("adds two numbers", () => {
  expect(add(2, 3)).toBe(5);
});

bun test packages/utils

📊 Bun vs Other Monorepo Tools

✅ Final Thoughts

Working with Monorepos with Bun offers a blend of speed, simplicity, and modern tooling that fits naturally into today’s JavaScript workflows. Whether you're building a full-stack app or managing shared libraries, Bun's workspace support gives you everything you need with almost no configuration.

If you're tired of slow installs and complex setups, give Bun a try in your next monorepo project — you might not go back!

💡 Pro Tip: Use Bun for MVPs

Bun's speed and simplicity make it perfect for building MVPs or side projects that need quick iteration cycles. You’ll ship faster without sacrificing structure or maintainability.