Introduction

Introduction

Welcome to Bun for Beginners, a project-based approach to building web applications with Bun.

This book is for developers who are new to Bun: Node.js developers who want to see what Bun replaces, and newer full-stack developers who want to build a real app without assembling a large toolchain first.

You will start with a tiny HTTP server and grow it into a real app foundation with routing, forms, tests, SQLite, user accounts, sessions, authorization, search, pagination, and deployment.

Bun is a single, dependency-free binary that bundles several tools JavaScript and TypeScript projects usually install separately: a runtime, package manager, test runner, bundler, HTTP server, SQLite driver, and more.

Why this book exists

The Bun docs are excellent. They explain the APIs, show focused examples, and are the first place you should look when you need exact reference material.

This book has a different job. It gives you an order to learn Bun by building one app from an empty folder to a working full-stack project. You will build the app, run into the rough edges, fix them, and see how Bun's built-in features fit together.

Why Bun

Bun is interesting because it collapses several tools into one binary. That does not mean you never need other tools. It means you can start with fewer of them.

Simple mental model

Traditional stack:

Node + npm + Jest + Webpack + Express + dotenv + more...

Bun stack:

Bun

The Bun Way

Bun changes how you build applications by reducing the number of tools you need and simplifying the development workflow. In this book, we will follow a consistent approach:

• Start with working code quickly, not configuration
• Prefer built-in features before adding dependencies
• Build small, complete pieces instead of abstract systems
• Keep the stack minimal and understandable
• Add complexity only when it is needed

This approach keeps development fast, reduces errors, and makes it easier to understand how your application works.

Beyond the four pillars, Bun includes several built-in features that further reduce the need for dependencies:

• HTTP server — replaces basic use of Express
• SQLite driver — no external database client needed for local apps
• Environment variable handling — replaces dotenv-style packages
• File and system utilities — fewer helper libraries
• Image manipulations like resizing, rotation, and format conversion

We will use most of these as we build through the book.

Why Learn Bun?

Because Bun is no longer just "the fastest JavaScript runtime." It is becoming a practical default for small teams and solo builders who want fewer moving parts. It collapses a messy toolchain into one product, and in most cases, does it faster than the tools it replaces. Bun is quickly becoming a serious alternative to the traditional Node.js toolchain, especially for small and focused projects.

Prerequisites

You do not need previous experience with Node, Bun, or even web development to complete this book. The goal is to help you quickly gain confidence building real applications with Bun.

That said, familiarity with basic JavaScript or TypeScript, along with HTML and CSS, will help you understand the concepts more quickly.

When appropriate, we will reference alternative tools and approaches so you can see how Bun reduces complexity and, in many cases, improves performance.

Book Structure

This book follows a project-based approach. Each chapter builds on the previous one, introducing new concepts through real applications rather than isolated examples.

You will start with a tiny HTTP server running on your own computer and grow it into a real app foundation with routing, forms, tests, SQLite, user accounts, sessions, authorization, search, pagination, and deployment.

The goal is to build confidence by working through small, complete pieces that grow into a production-ready application.

By the end of the book, you will have built a full web application locally and then deployed it so it can be reached from other computers.

Book Layout

This book includes shell commands and code examples throughout.

Shell commands: bun --version

bun run index.ts

TypeScript code:

const server = Bun.serve({
  port: 3000,
  routes: {
    "/": () => new Response("Run from Bun!"),
  },
});

New or changed lines in code examples will be marked with a comment:

const server = Bun.serve({
  ...
  console.log(`Listening on ${server.url}`);
});

Local Development and Real Websites

For most of this book, you will run the app on your own computer. When you start the server and visit localhost, your browser is talking to a program running locally on your machine. That is perfect for learning and development, but it also means someone on another computer cannot normally visit your app.

A real public website works the same way: the application runs on a computer connected to the internet, and other people’s browsers connect to that computer when they visit the site. That computer is usually called a server.

A server does not have to be a machine sitting in your house or office. It is often a rented virtual private server, a cloud app platform, or another hosting service. The important idea is that the app must be running on a computer with public internet access, usually behind a domain name like example.com.

We will keep things local while we build the app. Later, in Part III, we will deploy it so other people can access it from their own computers.

Advice on Getting Stuck

You will get stuck. Do not let it stop your progress. Often, stepping away for a bit or even sleeping on a problem can make it much easier to solve.

If you get stuck on a specific example or project in this book:

• Check our feedback forum to see if it has already been reported or discussed
• Watch for small typos, even if you think everything is correct
• Try copying the code directly from the source and running it again

Getting stuck is part of the process. The key is to keep moving forward.

About the Author

Brian has been building software since the late 1990s and has worked across multiple generations of web technologies. He co-founded Eyespike Corporation in 2002 and has been involved in building and maintaining production systems, including large-scale web applications.

Throughout his career, he has focused on practical, real-world development and staying current with evolving tools and approaches. His interest in Bun comes from its ability to simplify modern JavaScript development while improving performance.

This book is part of his effort to give back by helping developers build real applications with modern tools in a clear and practical way.

Conclusion

In the next chapter, we will set up your development environment and prepare your system for building more complete applications with Bun.