Bun — The New JavaScript Runtime That's Faster Than Node.js

The JavaScript runtime landscape has been dominated by Node.js for over a decade. Deno arrived in 2020 with fresh ideas about security and developer experience, but it never truly displaced Node.js in production environments. Now, Bun has entered the arena with an audacious claim: it wants to be a drop-in replacement for Node.js that is dramatically faster at virtually everything.

After Bun 1.0 launched in September 2023, we at StrikingWeb spent weeks benchmarking it against our existing Node.js workflows, testing compatibility with our project templates, and evaluating whether it is ready for production use. Here is what we found.

What Exactly Is Bun?

Bun is an all-in-one JavaScript runtime, bundler, transpiler, and package manager. Built from scratch using the Zig programming language and powered by Apple's JavaScriptCore engine (the same engine that powers Safari), Bun was designed from the ground up for speed.

Unlike Node.js, which relies on Google's V8 engine, Bun chose JavaScriptCore because it starts up faster and has more aggressive optimization for certain workload patterns. The result is a runtime that can execute JavaScript and TypeScript with remarkably low overhead.

What makes Bun unique is its scope. It is not just a runtime — it is an entire toolkit:

• Runtime: Execute JavaScript and TypeScript files directly, with no configuration needed
• Package Manager: Install npm packages up to 25 times faster than npm itself
• Bundler: Bundle JavaScript and TypeScript files for production with native speed
• Test Runner: Run tests with a Jest-compatible API at dramatically higher speeds
• Transpiler: Native TypeScript and JSX support without any additional tooling

Performance Benchmarks: How Fast Is Bun Really?

Speed claims are meaningless without real-world testing. We ran Bun through several benchmarks that reflect our actual development workflows.

Package Installation

We tested installing the dependencies of a typical Next.js project with approximately 1,200 packages. The results were striking:

• npm: 42 seconds
• yarn: 28 seconds
• pnpm: 18 seconds
• bun install: 3.2 seconds

Bun's package manager uses a global module cache, hardlinks instead of copies, and a highly optimized dependency resolution algorithm written in native code. The speed difference is not marginal — it is transformative, especially in CI/CD pipelines where dependency installation is a significant bottleneck.

HTTP Server Performance

Using a simple HTTP server that returns a JSON response, we measured requests per second:

• Node.js (native http): ~48,000 req/s
• Bun.serve(): ~132,000 req/s

Bun's built-in HTTP server, Bun.serve(), uses an event loop built on top of system-level APIs like epoll and kqueue, bypassing many of the abstractions that slow down Node.js.

TypeScript Execution

One of Bun's most developer-friendly features is native TypeScript execution. While Node.js requires a separate transpilation step (via ts-node, tsx, or a build step), Bun runs TypeScript files directly:

There is no tsconfig requirement for basic usage, no build step, and no waiting. For developers who have suffered through slow TypeScript compilation cycles, this alone is a compelling reason to consider Bun.

Node.js Compatibility

Bun's value proposition hinges on being a drop-in replacement for Node.js. In practice, compatibility is good but not perfect. Bun supports the vast majority of Node.js built-in modules, including fs, path, http, crypto, stream, and child_process. It reads package.json, supports npm scripts, and even respects node_modules resolution.

In our testing, most Express.js applications ran without modification. However, we encountered edge cases with certain native add-ons (N-API modules that rely on V8-specific internals) and some lesser-used Node.js APIs like vm and worker_threads behave slightly differently.

"For new projects, Bun is ready. For existing production Node.js applications, we recommend thorough testing before migration, particularly around native modules and streaming edge cases."

The Built-In Bundler

Bun ships with a native bundler that aims to compete with esbuild and webpack. It supports code splitting, tree shaking, and various output formats (ESM, CJS, IIFE). While it is not yet as feature-rich as webpack in terms of plugin ecosystem, its speed is remarkable — bundling a medium-sized React application takes under a second.

For teams that currently rely on esbuild for its speed, Bun's bundler offers a comparable experience with the advantage of being integrated into the same tool they use for everything else.

The Test Runner

Bun includes a built-in test runner with a Jest-compatible API. This means you can often run your existing Jest tests with bun test without modifying the test files:

In our benchmarks, Bun's test runner executed a suite of 400 unit tests in 1.8 seconds, compared to 12.4 seconds with Jest. The speedup comes from eliminating the separate transpilation step and using Bun's faster module resolution and startup time.

Where Bun Falls Short (For Now)

Despite its impressive performance, Bun has several areas where it still lags behind the mature Node.js ecosystem:

• Windows support: At the time of writing, Bun's Windows support is experimental. If your development or deployment environments include Windows, this is a significant limitation.
• Native modules: Some popular npm packages that use native C++ add-ons may not work correctly. The Bun team is actively working on improving N-API compatibility, but it is not 100 percent there yet.
• Production maturity: Node.js has been battle-tested in production for over 14 years. Bun 1.0 is new, and while it is impressive, it does not yet have the same track record of stability under extreme production workloads.
• Debugging tooling: Chrome DevTools integration and VS Code debugging support are still maturing for Bun.

Our Recommendation at StrikingWeb

We have started using Bun in specific parts of our workflow where its strengths are most impactful:

• CI/CD pipelines: Using bun install instead of npm has cut our dependency installation times by over 90 percent, saving minutes on every pipeline run.
• Local development scripts: Utility scripts, code generators, and development tooling now run through Bun for instant startup.
• New internal tools: For internal applications where we control the full stack, we are building with Bun's native HTTP server and test runner.
• Client projects: For client-facing production applications, we continue to use Node.js as the primary runtime while monitoring Bun's maturity closely.

The Bigger Picture

Bun's arrival is significant not just for what it offers today but for the competitive pressure it puts on the entire ecosystem. Node.js has already responded with performance improvements in recent versions, and Deno has accelerated its Node.js compatibility work. Competition is making every JavaScript runtime better.

For development teams, the takeaway is clear: the JavaScript runtime landscape is no longer a one-horse race. Bun is a legitimate contender that solves real pain points around speed and developer experience. Whether it becomes your primary runtime or a complementary tool in your workflow, it is worth your attention.

If you are evaluating Bun for your next project or considering a migration from Node.js, our team at StrikingWeb is here to help you make the right choice for your specific needs and constraints.