Bun vs ts-node

For years, ts-node led in executing TypeScript by offering dependable compilation via the official TypeScript compiler. Then Bun emerged, redefining the limits of what JavaScript runtimes can achieve.

ts-node has served as the trusted backbone for TypeScript development, allowing direct execution of TypeScript with integrated compiler support. It is the tool relied upon by millions of developers for ensuring type-safe workflows.

Bun offers a runtime experience, crafted from scratch in Zig and powered by JavaScriptCore's outstanding performance. It’s not just about running TypeScript more quickly—Bun truly enhances your whole development journey with built-in tools and exciting new features.

This detailed comparison examines how the reliable standard compares to the innovative newcomer that's shifting expectations in TypeScript development.

What is ts-node?

ts-node has been a fundamental tool for TypeScript development for many years, enabling direct execution of TypeScript code without the need for prior compilation.

Its power lies in its strong integration with the TypeScript compiler. It offers all the features of a full language server, such as complete type checking, decorator support, and broad TypeScript compatibility. This tight integration allows it to work seamlessly with the ecosystem and detect type errors during runtime.

In addition to running code, ts-node provides comprehensive development tools like REPL, a wide range of configuration options, and strong support for testing frameworks. It serves as a dependable foundation for numerous TypeScript projects.

What is Bun?

Bun is a runtime engineering method based on fundamental principles aimed at removing performance bottlenecks that have historically hampered JavaScript development.

Built with Zig and utilizing JavaScriptCore's remarkable speed, Bun provides TypeScript execution that surpasses traditional Node.js, making it feel sluggish in comparison. However, Bun is not only focused on performance; it also integrates package management, bundling, testing, and development servers into a smooth, all-in-one platform for development.

Bun vs. ts-node: comprehensive feature analysis

This choice is more than just picking a TypeScript runner. It's about choosing between proven reliability and cutting-edge performance and integration. Each option caters to different developer priorities and project needs.

Here's how these two approaches compare across every dimension that matters for TypeScript development.

Development workflow and TypeScript watch modes

The true test of any TypeScript tool isn't the first use. It's the 50th time you save a file and want to see changes instantly. This is when the development experience philosophies become really clear.

Bun's state-preserving hot reloading fundamentally transforms the experience:

# Bun TypeScript watch capabilities
bun --watch app.ts               # Fast process restart for TypeScript
bun --hot server.ts              # Hot reloading with state preservation

# What this means in practice:
# - Your HTTP server keeps running during TypeScript changes
# - Database connections stay alive
# - In-memory state survives code updates
# - Zero downtime during development iterations

Imagine updating your TypeScript API handler without losing your authenticated session or having to re-seed test data. That's the magic of Bun's hot reloading. It feels like editing a running program.

ts-node takes the battle-tested restart approach with external tooling:

# ts-node TypeScript watch setup
nodemon --exec "ts-node src/server.ts"

# Or with ts-node-dev for optimized reloads
ts-node-dev src/server.ts

# What this provides:
# - Reliable TypeScript file monitoring
# - Full type checking on every restart
# - Clean slate with each change
# - Predictable, debuggable behavior

While you lose application state with each restart, you gain the confidence that every reload includes complete type checking. No surprises, no hidden type errors. Just reliable, safe TypeScript execution.

TypeScript execution and runtime capabilities

The philosophical split is most clear when comparing how each tool handles your TypeScript code: one emphasizes speed, the other prioritizes safety.

Bun's transpilation-first philosophy gets you running fast:

// Bun TypeScript execution approach
enum ProjectStatus {
  Active = 'active',
  Inactive = 'inactive'
}

class TaskManager {
  private tasks: Task[] = [];

  addTask(task: Task): void {
    this.tasks.push(task);  // Transpiled and executed immediately
  }
}

// Bun strips types and runs, trusting your IDE for type safety

Bun assumes your editor is already catching type errors, so it focuses on getting your code running as quickly as possible. It's the "move fast and trust your tooling" approach.

ts-node's compilation-first philosophy catches errors before they become runtime problems:

// ts-node comprehensive TypeScript handling
interface Task {
  id: string;
  status: ProjectStatus;
}

class TaskManager {
  private tasks: Task[] = [];

  addTask(task: Task): void {
    this.tasks.push(task);  // Fully type-checked before execution
  }

  // ts-node stops execution here with detailed error
  addInvalidTask(task: string): void {  
    this.tasks.push(task); // Error: Argument of type 'string' not assignable
  }
}

ts-node acts as your safety net, catching type mismatches that might slip through during rapid development. It's the "measure twice, cut once" philosophy applied to TypeScript development.

ESM and module system compatibility

Modern TypeScript development increasingly relies on ES modules, and how each tool handles ESM reveals significant differences in their approach to contemporary JavaScript standards.

Bun provides native ESM support that just works out of the box:

# Bun handles all module formats seamlessly
bun modern-esm-app.ts            # Pure ESM TypeScript
bun mixed-modules.ts             # ESM importing CommonJS
bun legacy-commonjs.ts           # Traditional CommonJS

# TypeScript ESM imports work naturally
import { createServer } from './server.ts'    # .ts extension supported
import type { UserConfig } from './types.ts'  # Type-only imports

Bun's approach feels effortless because it understands that modern TypeScript projects use ESM by default. File extensions in imports work naturally, and mixing module formats creates no friction or configuration overhead.

ts-node's ESM support requires complex configuration and often frustrates developers:

# ts-node ESM requires specific Node.js flags
node --loader ts-node/esm app.ts
# Or with newer Node.js versions
node --import ts-node/esm app.ts

# Plus additional tsconfig.json setup
{
  "ts-node": {
    "esm": true
  },
  "compilerOptions": {
    "module": "ESNext",
    "moduleResolution": "node"
  }
}

The complexity doesn't end there. ts-node's ESM support often breaks with mixed module environments, forcing you to choose between CommonJS and ESM architectures instead of supporting both naturally. Many developers end up avoiding ESM with ts-node simply because the setup friction isn't worth the hassle.

This difference becomes particularly important when working with modern TypeScript frameworks and libraries that assume ESM by default. Bun lets you adopt contemporary patterns immediately, while ts-node often requires architectural compromises or extensive configuration workarounds.

REPL and interactive TypeScript development

When you need to quickly test a TypeScript concept or debug a complex type interaction, the REPL becomes your most valuable tool. Here, the winner is obvious.

ts-node's full-featured TypeScript REPL makes interactive development a joy:

# ts-node feature-rich TypeScript REPL
npx ts-node
> interface User { name: string; age: number; }
> const user: User = { name: 'Alice', age: 30 }
> user.name    # IntelliSense suggests properties
'Alice'
> user.age = 'thirty'  # Immediate, helpful error feedback
# Error: Type 'string' is not assignable to type 'number'

This isn't just a JavaScript REPL with TypeScript syntax. It's a fully-featured TypeScript environment where you can experiment with interfaces, test generic constraints, and debug complex type scenarios interactively.

Bun's JavaScript-only REPL leaves TypeScript developers in the cold:

# Bun REPL limitations for TypeScript
bun repl                        # JavaScript REPL only
# interface User { name: string } // Syntax error
# Must create .ts files for any TypeScript experimentation

This gap is particularly frustrating when you're learning TypeScript or debugging type issues. You end up creating throwaway .ts files instead of experimenting interactively, breaking the flow of exploratory programming.

TypeScript testing capabilities

Testing TypeScript code reveals another fundamental difference: integrated simplicity versus ecosystem maturity.

Bun's zero-configuration TypeScript testing removes friction entirely:

# Bun TypeScript testing
bun test                         # Finds and runs .ts test files automatically
bun test --watch                 # Instant feedback on TypeScript test changes
bun test --coverage              # Coverage reports for TypeScript source

# What this means for your workflow:
# - No jest.config.js or test setup
# - TypeScript tests run at native speed
# - Built-in mocking works with TypeScript modules

Write a .test.ts file, run bun test, and everything just works. No configuration files, no preset selection, no TypeScript compilation pipeline to set up.

ts-node's ecosystem-integrated approach offers maximum flexibility but requires setup:

# ts-node TypeScript testing integration
jest --preset ts-jest           # Mature Jest integration for TypeScript
mocha -r ts-node/register 'test/**/*.ts'  # Mocha with TypeScript support

# What this provides:
# - Full type checking during test execution
# - Detailed error reporting with TypeScript context
# - Extensive plugin ecosystem
# - Battle-tested debugging capabilities

While requiring more initial setup, ts-node's testing approach gives you the full power of mature testing frameworks with complete TypeScript integration. Your tests get the same rigorous type checking as your application code.

TypeScript configuration and setup

The onboarding experience reveals how each tool balances simplicity with control. This choice affects your entire team's adoption process.

Bun's convention-over-configuration approach gets you started in seconds:

# Bun TypeScript setup
curl -fsSL https://bun.sh/install | bash  # One-line install
bun run app.ts                           # Run any TypeScript file immediately

# Configuration when you need it:
# - Automatically reads tsconfig.json if present
# - Works perfectly without any configuration
# - Respects your TypeScript compiler options when provided

New team members can start contributing immediately. No configuration files to understand, no build processes to learn. TypeScript just works.

However, ts-node's explicit configuration approach gives you complete control over the TypeScript compilation process:

# ts-node TypeScript setup
npm install --save-dev typescript ts-node @types/node

# Thoughtful tsconfig.json configuration:
{
  "ts-node": {
    "transpileOnly": true,    # Skip type checking for speed
    "files": true,           # Include all project files
    "compilerOptions": {
      "target": "es2020",    # Control output target
      "module": "commonjs",  # Module system selection
      "esModuleInterop": true # Import compatibility
    }
  }
}

While requiring more upfront investment, this approach lets you fine-tune every aspect of TypeScript compilation. Teams with specific requirements or complex TypeScript setups appreciate this level of control.

Final thoughts

Bun wins decisively because it treats TypeScript as a first-class citizen, not an afterthought.

ts-node built the bridge that let millions of developers cross into TypeScript territory. Its REPL and ecosystem maturity remain genuinely impressive achievements.

But here's what changes everything: Bun doesn't just run TypeScript. It was designed with TypeScript in mind from day one. No external loaders, no registration hooks, no complex configuration. TypeScript files run natively, just like JavaScript.

When your runtime treats TypeScript as naturally as JavaScript, everything else flows from that design choice. The speed, the tooling, the developer experience. That's why Bun doesn't just run TypeScript faster; it makes TypeScript development feel effortless.

Got an article suggestion? Let us know

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.