Bun vs. Node.js: Is the New JavaScript Runtime Really Faster?

Originally published: September 11th, 2023. Updated on: April 29th, 2025.

JavaScript reigns as the world's most commonly used programming language. Node.js played a huge role in its wider adoption beyond the browser. But could a new JavaScript runtime shake things up?

If you follow JavaScript news, especially on platforms like X/Twitter, you've likely heard the buzz about Bun and claims of it being significantly faster than Node.js and Deno. But is it really?

What exactly is Bun? Is it a framework, a build tool, or a completely new runtime environment? And importantly, how might it impact the average developer's day-to-day experience?

Bun’s Performance – How Does Node.js Stack Up?

Bun 1.0 officially landed on September 8th, 2023, after two years in development by Jared Sumner, generating considerable excitement within the JavaScript community. Frankly, it's an audacious attempt to redefine much of what we know about current JavaScript tooling. It promises blazing-fast performance and a fresh take on common development tasks. Some even speculate it could dethrone the mighty Node.js, a true behemoth in the ecosystem. (While other runtimes like Deno exist, this article focuses primarily on the Node.js comparison).

So what exactly is Node.js?

Before diving into Bun, let's quickly recap what Node.js is and does. Node.js acts as the backbone for countless web servers, APIs, real-time apps, and CLI tools across the internet. Even desktop applications built with frameworks like Electron (powering widely used tools like VS Code and Slack) rely on Node.js. Major companies leverage Node.js extensively:

• Netflix: Uses Node.js server-side to streamline performance for its 230 million subscribers.
• LinkedIn: Runs its mobile backend on Node.js, reportedly cutting server requirements down to 10%.
• Trello: Utilizes Node.js for server-side operations, managing vast numbers of simultaneous connections for collaboration.
• Walmart: Rebuilt its mobile app (accessed by 120 million users monthly) using Node.js.

So, yeah, having a new runtime like Bun emerge to challenge Node.js's crown is a pretty big deal.

So, What’s This Bun Runtime All About?

Bun is a new JavaScript runtime, built from the ground up, designed to make JavaScript development and processing quicker and easier.

The goal of Bun is to run most of the world’s server-side JavaScript and provide tools to improve performance, reduce complexity, and multiply developer productivity – bun.sh

Essentially, Bun is designed as a drop-in replacement for Node.js, aiming to handle many of the tasks Node.js currently performs. It targets the server-side, the behind-the-scenes computers powering large-scale operations, not the JavaScript running in your browser.

Plug and Play

The aim is for Bun to integrate seamlessly into the existing JavaScript ecosystem, making developers' lives simpler. It's not intended to introduce new problems, though the smoothness of any transition always remains to be seen with new tools!

What makes Bun different from Node.js boils down to a few key points:

1. It uses a different JavaScript engine.
2. It's written in a newer, potentially more efficient language.
3. It handles external code (dependencies) differently.
4. It aims to fix a long-standing developer complaint.

Let's dig into these.

Apple’s JavaScriptCore – Bun Runtime’s Engine

Unlike Node.js, which runs on Google Chrome's V8 engine, Bun utilizes JavaScriptCore (JSC), the engine powering Apple's Safari browser.

Chrome’s V8 Engine

V8, the heart of Node.js, is the most widely used JavaScript engine. Most users aren't even aware of it working behind the scenes in Chrome and Chromium-based browsers (like Brave, Opera, Edge). V8 is far from ancient; it's fast, efficient, and constantly updated. Its speed and non-blocking I/O model (allowing parallel task execution) are cornerstones of Node.js's success.

Safari’s JavaScriptCore Engine – powering Bun

Bun, running on JavaScriptCore, brings a different set of potential advantages. JSC is optimized for macOS and iOS, ensuring tight integration with Apple hardware. Apple invests heavily in JSC's development, meaning Bun leverages a mature and optimized engine. However, it's not currently optimized for Windows, though developers can use the Windows Subsystem for Linux (WSL) to run it effectively on Windows machines.

Programming Languages: Zig vs. C/C++

Node.js was created in 2009 by Ryan Dahl using C/C++. C++ builds on C, a language dating back to 1972—an industry staple, but one carrying significant historical baggage, especially concerning memory management.

Bun, conversely, is written in Zig, a much newer language created by Andrew Kelley in 2016. Zig is known for its efficiency, safety features, and low-level memory control, giving developers more leverage over system resources.

Zig & Bun

Zig's modern approach allows Bun's creators to explore more efficient processes, leading to the impressive performance benchmarks that have generated so much hype. C/C++, being older, makes manual memory management more challenging. Furthermore, V8 was designed with JavaScript's ease-of-use in mind, incorporating garbage collection—a process where the engine automatically reclaims unused memory. While this simplifies development, garbage collection can introduce performance pauses and unpredictability.

Zig’s design helps Bun avoid reliance on traditional garbage collection. This spares Bun the unpredictable pauses and allows for a potentially more streamlined execution path, giving it a significant performance boost.

Performance Testing: Bun vs Node vs Deno

So, how much faster is Bun in practice? Benchmarks offer some clues:

• SQLite Database Access (Queries per second):
  • Bun: 81 (average)
  • Deno: 43 (~2x slower)
  • Node.js: 21 (~4x slower)
• HTTP Requests per second (100 concurrent connections):
  • Bun: 110,000
  • Deno: 67,000 (~60% as fast)
  • Node.js: 59,000 (~50% as fast)

Impressive results, right? Bun consistently comes out at least 2x faster than its rivals in these tests.

The Node.js Garbage Problem

Why hasn't Node.js adopted similar techniques? A major factor is its reliance on V8 and its garbage collection mechanism. While garbage collection simplifies development, it introduces performance overhead.

Historically, when V8 was created in 2008, manual memory management in languages like C/C++ was complex, and many popular languages (Java, C#, Python, Ruby) used garbage collection.

Today, however, languages like Rust (which Deno uses) employ techniques like ownership/borrowing to ensure memory safety at compile time, often avoiding runtime garbage collection. Better development tools, static analysis, more available learning resources, and larger support communities also make manual or compile-time memory management more feasible now. The timing seems right for a new player like Bun, built with a modern language like Zig, to offer a faster approach.

Could Node.js Make the Same Improvements?

Retrofitting Node.js for similar performance gains would be a monumental task. Its deep coupling with V8, an engine designed with garbage collection, would require major architectural changes or a complete engine swap. Plus, many developers value Node.js's proven stability and reliability, and might resist the upheaval required for such changes, even for performance gains. Time will tell if Bun's growth prompts further optimization efforts within the Node.js ecosystem.

Package Management and Bundling

JavaScript developers are intimately familiar with Node.js and its infamous node_modules folder. This folder stores all project dependencies downloaded by the Node Package Manager (npm). npm manages these external libraries, fetching them from remote repositories.

However, Node.js itself is not a bundler. Bundlers (like Webpack, Rollup, Parcel) optimize and compress all these separate dependency packages into fewer, smaller files for deployment. Historically, Node.js has relied on these external tools. The sheer size of the node_modules folder has also become a long-running joke among developers due to its often enormous and bulky nature.

Bun Runtime & Bundler

Bun aims to simplify this: it is both a runtime and a bundler. It offers the complete package—executing JavaScript code and managing/optimizing dependencies.

Bun also boasts more streamlined package management. It claims to install packages faster by fetching them in parallel and potentially including only the necessary parts of each package. Having the bundler built-in offers several advantages:

• Tighter Integration: More efficient processes tailored to the runtime.
• Consistency: Less worry about incompatibilities with external tools.
• Simplified Toolkit: One less external tool to manage.
• Faster Iteration: Easier to roll out improvements for both runtime and bundler together.

ESM vs CommonJS: Fixing a Headache?

Modern JavaScript relies heavily on modules—chunks of reusable code often sourced from third-party repositories. Historically, managing these modules was messy. Developers initially devised their own standard (CommonJS, using require() and module.exports), before JavaScript officially implemented its own module system (ESM or ECMAScript Modules, using import and export).

Node.js tried to support both, leading to a somewhat clumsy implementation involving different file extensions (.cjs for CommonJS, .mjs for ESM) and often requiring bridging code, causing conflicts and confusion. This has been a massive headache for developers.

Bun attempts to fix this by fully embracing ESM while also providing an easier way to import CommonJS modules. If Bun can truly unite these two systems seamlessly, it would be a huge win.

But Wait... What Makes Node.js So Great Anyway?

Let's pause and appreciate why Node.js holds its current position.

Simply put, Node.js allows JavaScript to run outside the web browser.

JavaScript started in 1995 purely as a browser language, designed to add interactivity to web pages. For a long time, that was its primary role. Eventually, it evolved into the powerful language we know today, capable of complex data flows, server communication, and even 3D graphics rendering within the browser.

Node.js was created to essentially let JavaScript "escape" the browser, bringing its power to server-side scripting, databases, command-line tools, and more—tasks previously dominated by other languages. This had a massive impact, making Node.js a highly sought-after skill almost overnight. It enabled JavaScript developers to build:

• Server-side applications with database and filesystem access.
• Command-line tools and task runners (like Gulp, Grunt).
• Real-time applications (using libraries like Socket.IO).
• Desktop applications (via frameworks like Electron).
• Internet of Things (IoT) devices.

Bun Shouldn’t Be Dismissed Lightly

Understanding Node.js's impact highlights why a potential challenger like Bun is such a big deal. Any tool threatening Node.js's dominance has the potential to significantly reshape the technology landscape. The possibility of Bun replacing much of what Node.js does is huge. While a complete replacement seems unlikely, Bun will certainly challenge Node.js's #1 spot in job listings and tech stacks.

Quality of Life Improvements

One significant area where Bun could win is simply by making developers' lives easier. Waiting for server-side tasks (like framework bundling/compiling, CSS/script reloading, dependency installs/updates) is a common part of the daily routine. Even shaving a few seconds off each repetitive task adds up to significant time savings, a welcome efficiency gain for any developer. This alone could give Bun a considerable advantage.

Node.js Has Earned Its Place

Despite Bun's potential, Node.js benefits from being an extremely battle-hardened system, proven over countless hours in demanding production environments. Large companies are often slow to move away from tried-and-tested solutions, prioritizing stability and profit over developer convenience.

Upsetting the Apple Cart?

Bun's use of Apple's JavaScriptCore engine could also have broader implications. It might boost Safari's profile among developers, potentially increasing competition in the browser space currently dominated by Chrome. Some argue Chrome's dominance has led to stagnation in web standards, so increased competition could revitalize this crucial area.

Job Opportunities

A shift towards Bun could diversify job opportunities for server-side JavaScript developers, moving away from Node.js as the default. On the flip side, this means more technologies for developers to keep track of—the life of a modern web dev is one of constant learning! Regardless, having a new contender like Bun is exciting for the future of JavaScript development.

Skepticism is Welcome

With any new technology hype, it's important to maintain perspective. Bun still needs to prove itself in scalable, high-pressure, real-world environments with a larger developer base. Time will tell if the impressive early benchmarks translate to similar real-world gains. Even so, a small performance boost, especially bundled with reduced complexity, would be welcome.

Node vs Bun: The Decision

Ultimately, developers and teams face a choice: stick with the proven Node.js or embrace the newcomer, Bun?

As Shalini Tewari noted on X/Twitter: Bun prioritizes speed and efficiency with built-in tools and the JSC engine, while Node.js offers a larger community, broader language support (via external tools), and the V8 engine. It's not as clear-cut as raw performance metrics might suggest.

Bun Has Big Shoes to Fill

The vast JavaScript ecosystem relies heavily on packages built primarily for Node.js. Bun faces the mammoth task of ensuring compatibility or providing a smooth migration path for developers already wary of the "next big thing" promising to solve everything.

Early reports suggest Bun 1.0 still has bugs and compatibility issues with various packages. While exciting, it's likely not quite ready for widespread production deployment just yet. Experimentation is encouraged, but switching critical production systems requires caution until the kinks are ironed out.

Bun certainly has the potential to be the next big thing in JavaScript. But it also risks becoming just another tool in the ever-expanding developer toolkit. To truly challenge Node.js, it needs to deliver a knockout punch.