What Do Deno and Bun Bring to the Table?

Antonello Zanini

Antonello Zanini on

What Do Deno and Bun Bring to the Table?

Deno and Bun are two JavaScript runtime newcomers that aim to undermine Node.js. These alternatives have gained popularity for their innovative approach to server-side development with JavaScript. But the real question is: what do they bring to the table compared to Node.js?

In this post, you'll learn what Deno and Bun are, what they offer, and how they address some long-standing drawbacks in Node.js. We'll shed light on specific use cases where Deno and Bun excel.

Join us on this journey to discover the potential of Deno and Bun!

Introducing JavaScript Runtimes

A JavaScript engine is a software component responsible for parsing JavaScript, converting it into executable code, and running it. This technology is at the core of every browser.

At the time of writing, there are three main JavaScript engines:

  • V8: Developed by Google to support Chrome and Chromium.
  • SpiderMonkey: Maintained by the Mozilla Foundation for Firefox.
  • JavaScriptCore: Created by Apple for WebKit implementations, such as Safari.

About Node.js, Deno, and Bun: A Brief History

In 2009, Ryan Dahl began work on a JavaScript runtime that would enable JavaScript to run outside the browser. The specific runtime was Node.js and it was built around V8.

Since then, Node.js has become the go-to technology for frontend and backend development. At the same time, the technology originally had some limitations. Plus, many modern JavaScript standards like Fetch API and ES modules didn’t exist.

Ryan Dahl then decided to begin work on a Rust-based successor to Node.js. In 2018, he released Deno, a JavaScript runtime focused on speed, robust standards, and TypeScript support. Similarly, in 2022, Jarred Sumner unveiled Bun, a JavaScript runtime developed in Zig. Bun is very fast and it ensures compatibility with Node.js APIs to simplify code migration.

The main purpose of Deno and Bun is to allow the execution of JavaScript outside of a browser, especially on the backend.

Let’s now see the distinct features and capabilities offered by the two technologies.

About Deno

Deno is a secure, modern, and standard-compliant JavaScript and TypeScript runtime built in Rust.

⚙️ Main Features and Characteristics of Deno

  • Native TypeScript support: Developers can write and run TypeScript code seamlessly.
  • Permission APIs: A built-in system for enforcing fine-grained permissions to control what scripts are allowed to do.
  • Rust core: The runtime core is written in Rust, a language known for its reliability and performance.

👍 Pros

  • Security: Deno is secure by default, thanks to its permission model.
  • TypeScript integration: TypeScript is supported natively without the need for additional setup or tools.
  • Compliance with web standards: Deno embraces modern JavaScript features and standards, trying to provide the same APIs offered by browsers.

👎 Cons

  • Small ecosystem: There are only a few thousand third-party Deno models available.
  • Migration challenges: Migrating existing Node.js projects to Deno may require considerable adjustments because of the significant differences between the two projects.

About Bun

Bun is a new, lightning-fast, standard-oriented JavaScript/TypeScript runtime built with the Zig programming language.

⚙️ Main Features and Characteristics of Bun

  • Based on JavaScriptCore: Instead of Google’s V8 JavaScript and Web Assembly engine, Bun relies on the faster and more efficient JavaScriptCore.
  • More control: Zig is a low-level language that provides great control over code execution.
  • npm-compatible package manager: Bun can install npm packages 20 times to 100 times faster than npm install.

👍 Pros

  • Node.js compatibility: Bun is designed to work with existing Node.js codebases.
  • Performance: JavaScript is executed as fast as possible, up to 4 times better than Node.js.
  • Web standards: Bun implements the most widely adopted web standard APIs, such as the Fetch API and WebSocket API.

👎 Cons

  • Limited adoption: The technology is relatively new. The roadmap still involves many key features and the tool doesn’t yet have a large user base or ecosystem.
  • Zig popularity: Zig isn’t as well known as JavaScript or Rust, which may impact community contributions and support.

But Wait, Why Wasn't Node.js Enough?

Node.js wasn’t actually the first JavaScript runtime to run JS server-side. It was the first to be adopted globally, but is that enough to make it perfect as a technology? No way!

Node.js comes with some well-known flaws, limitations, and issues. These have allowed for the growth of alternative JavaScript runtimes such as Deno and Bun.

It's time to dig into the drawbacks of Node.js and find out how Deno and Bun plan to address them!


Node.js is single-threaded, which means it can only use one CPU core at a time. While it is designed to handle asynchronous I/O operations, that can lead to performance bottlenecks with CPU-intensive tasks.

Since Deno is based on the same JavaScript engine, it offers comparable performance. The main difference lies in Rust's high efficiency and resource utilization capabilities. This enables Deno to be slightly faster and have better CPU and memory utilization than Node.js.

However, Bun has put speed at the very top of its list of goals. Thanks to Bun's JavaScriptCore engine and Zig programming language, it can perform significantly better than Deno and Node.js.

TypeScript Support

Node.js doesn’t natively support TypeScript. To use TypeScript in Node.js, you need to set up transpilation and execution tools. This additional setup takes time, isn't always easy, and may introduce numerous challenges.

Both Deno and Bun offer first-class integrated TypeScript and JSX support. Developers have the ability to write and run TypeScript code seamlessly. This removes the need for extra tools, providing a better development experience.


Node.js itself is quite secure and has no known significant vulnerabilities. Unfortunately, the same can’t be said for the hundreds of thousands of npm libraries available. The main issue is that the permission mechanism is still experimental at the time of writing. That will support marking loaded resources as untrusted or trusted for added security.

Deno prioritizes security with its robust permission system that enforces strict access controls. For example, a script must be explicitly granted permission to access specific resources. By default, a Deno script has no access to files, the network, or the environment. That reduces the likelihood of unauthorized access.

In contrast, as Bun offers backward compatibility to Node.js, it also inherits all its security issues. Bun's emphasis on performance may lead the community to focus on speed over security. The team behind it hasn’t yet focused on this drawback.

Compliance with Web Standards

Node.js was initially designed for server-side JavaScript and has ignored most browser standards. In recent years, the community has worked hard to address this problem, but you can still experience misalignment when running the same JS code on both Node.js and the browser.

Deno and Bun were born years after Node.js, when web standards had already become popular. Thus, they have both prioritized the implementation of those standards since day one. This makes code written in Deno and Bun easier to translate for browsers and vice versa.

Will Deno or Bun Replace Node.js?

No, Deno and Bun won't replace Node.js, for several compelling reasons:

  • The extensive npm ecosystem has solidified Node.js in the web development landscape.
  • Transitioning to a new technology always involves some migration challenges.
  • Companies aren't likely to abandon their investments in Node.js for less mature technologies.
  • Performance and security improvements aren't enough to justify the switch.
  • Finding Deno and Bun developers is way harder than finding Node.js developers.

What's for sure is that the Node.js team won't sit on their hands while Deno and Bun carve out a slice of the market. Quite the contrary: they'll take inspiration from the key features offered by their competitors for future improvements.

So, Deno and Bun aren't bound to retire Node.js, and that’s perfectly fine!

Their goal shouldn’t be to compete with Node.js, but to become a viable alternative for specific use cases and requirements. For example, Deno is appealing for projects where security is paramount. Bun, on the other hand, is more suitable for performance-oriented applications.

Deno and Bun should be considered complementary solutions to Node.js that can coexist within the broader JavaScript ecosystem.

Wrapping Up: Deno and Bun, the JavaScript Runtimes of the Future!

In this blog post, we looked at what Deno and Bun bring to the table of JavaScript runtimes.

You now know:

  • How we went from Node.js to Deno, and then to Bun
  • What Deno is and what it has to offer
  • What Bun is and what it has to offer
  • The drawbacks of Node.js and how Deno and Bun address some of these drawbacks

Thanks for reading!

P.S. If you liked this post, subscribe to our JavaScript Sorcery list for a monthly deep dive into more magical JavaScript tips and tricks.

P.P.S. If you need an APM for your Node.js app, go and check out the AppSignal APM for Node.js.

Antonello Zanini

Antonello Zanini

Guest author Antonello is a software engineer, but prefers to call himself a Technology Bishop. Spreading knowledge through writing is his mission.

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