Bun vs Deno vs npm: Runtime and Package Management Compared

When building JavaScript applications today, you have three main options for managing dependencies and running your code. npm is the established package manager for Node.js. bun and deno are complete runtime environments with built-in package management. Let's compare how they handle real-world development tasks.

📦 Installing Packages: Different Approaches

npm requires Node.js and installs packages to a node_modules folder.

• Uses a package.json file to track dependencies
• Creates a lockfile (package-lock.json) for consistent installs
• Well-understood behavior after years of use

# npm: Install a package
npm install express

# npm: Install with specific version
npm install lodash@4.17.21

# npm: Install dev dependency
npm install --save-dev jest

bun installs packages much faster with a global cache.

• Compatible with existing package.json files
• Creates bun.lockb (binary lockfile) for speed
• Can install npm packages directly

# bun: Install a package
bun add express

# bun: Install with specific version
bun add lodash@4.17.21

# bun: Install dev dependency
bun add -d jest

deno uses URLs or npm specifiers with explicit permissions.

• No node_modules folder - caches modules globally
• Uses deno.json or import_map.json for dependency management
• Requires permission flags for network, file system access

# deno: Run with npm package
 deno run --allow-read --allow-net npm:express

# deno: Install using deno.json
# In deno.json:
{
  "imports": {
    "express": "npm:express@4.18.2"
  }
}

# Then import in code:
import express from "express";

🔒 Security Model: Trust vs Permissions

npm runs with full system access by default.

• Packages can access files, network, and environment variables
• Security relies on trusting package authors
• No built-in permission system

// npm/Node.js: Full access by default
const fs = require('fs');
const data = fs.readFileSync('/etc/passwd'); // Works without warning

bun follows Node.js compatibility with similar access.

• Default behavior matches Node.js for compatibility
• Working on permission features but not fully implemented
• Best for trusted codebases

// bun: Similar to Node.js
import { readFileSync } from 'fs';
const data = readFileSync('/etc/passwd'); // Works by default

deno requires explicit permissions for sensitive operations.

• Must declare what your code can access
• Prevents accidental security issues
• More verbose but safer for untrusted code

// deno: Requires permission flag
// Run with: deno run --allow-read script.ts
const data = await Deno.readTextFile('/etc/passwd');
// Without --allow-read, this throws permission error

🚀 Running Code: Entry Points and Execution

npm requires Node.js and a JavaScript entry file.

• Use node command to run scripts
• Configure scripts in package.json
• TypeScript requires additional setup

// npm: package.json scripts
{
  "scripts": {
    "start": "node src/index.js",
    "dev": "nodemon src/index.js",
    "build": "tsc"
  }
}

# npm: Run your code
npm start
npm run dev

bun runs JavaScript and TypeScript directly.

• No separate TypeScript compilation step needed
• Single command for running, bundling, testing
• Faster startup than Node.js

# bun: Run TypeScript directly
bun run src/index.ts

# bun: Run with hot reload
bun --watch src/index.ts

# bun: Run tests
bun test

deno runs TypeScript natively with security flags.

• Built-in TypeScript compiler
• Permission flags required for most operations
• Single executable for all tasks

# deno: Run TypeScript
 deno run --allow-net src/index.ts

# deno: Run with watch mode
 deno run --watch --allow-net src/index.ts

# deno: Run tests
 deno test

📁 Project Configuration Files

npm uses package.json for all project metadata.

• Dependencies, scripts, and project info in one file
• Widely supported by all tools
• Can become large and complex

// npm: package.json
{
  "name": "my-app",
  "version": "1.0.0",
  "scripts": {
    "start": "node index.js",
    "test": "jest"
  },
  "dependencies": {
    "express": "^4.18.0"
  },
  "devDependencies": {
    "jest": "^29.0.0"
  }
}

bun uses package.json with optional bunfig.toml.

• Compatible with existing npm projects
• Additional config for Bun-specific features
• Simpler migration from npm

# bun: bunfig.toml (optional)
[install]
exact = true

[test]
coverage = true

deno uses deno.json for configuration.

• Combines package.json and tsconfig.json functionality
• Cleaner separation of concerns
• Newer standard with growing adoption

// deno: deno.json
{
  "name": "my-app",
  "version": "1.0.0",
  "tasks": {
    "start": "deno run --allow-net src/index.ts",
    "test": "deno test"
  },
  "imports": {
    "express": "npm:express@4.18.2"
  },
  "compilerOptions": {
    "strict": true
  }
}

🧪 Testing: Built-in vs External Tools

npm requires external test frameworks.

• Install Jest, Mocha, or Vitest separately
• Configuration files needed
• More setup but more options

// npm: Jest test file
// test/example.test.js
const sum = require('../src/sum');

test('adds numbers', () => {
  expect(sum(1, 2)).toBe(3);
});

# npm: Run tests
npm test

bun has a built-in test runner.

• No additional dependencies needed
• Jest-compatible API
• Faster test execution

// bun: Built-in test
// test/example.test.ts
import { expect, test } from 'bun:test';

test('adds numbers', () => {
  expect(1 + 2).toBe(3);
});

# bun: Run tests
bun test

deno has a built-in test runner.

• No external dependencies
• Simple assertion library included
• Permission flags apply to tests too

// deno: Built-in test
// test/example_test.ts
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

Deno.test("adds numbers", () => {
  assertEquals(1 + 2, 3);
});

# deno: Run tests
 deno test

🌐 npm Package Compatibility

npm is the source of truth for package compatibility.

• All packages published to npm registry
• Full compatibility guaranteed
• No translation layer needed

# npm: Any npm package works
npm install any-npm-package

bun supports npm packages with high compatibility.

• Uses npm registry directly
• Some native modules may have issues
• Most popular packages work without changes

# bun: Install npm packages
bun add express react lodash
# Most packages work identically to npm

deno supports npm packages through compatibility layer.

• Use npm: specifier prefix
• Not all packages work perfectly
• Best for newer projects or Deno-native packages

// deno: Import npm packages
import express from "npm:express@4.18.2";
import _ from "npm:lodash@4.17.21";
// Some packages may have compatibility issues

📊 Summary: Key Differences

🌱 Shared Capabilities

Despite their differences, all three tools share important capabilities:

1. 📦 Package Management

All three can install and manage JavaScript dependencies from the npm registry.

# All can install express
npm install express
bun add express
deno run --allow-net npm:express

2. 🔧 Script Running

All support running custom scripts for development workflows.

// npm: package.json scripts
{ "scripts": { "build": "..." } }

// bun: package.json or bunfig.toml
{ "scripts": { "build": "..." } }

// deno: deno.json tasks
{ "tasks": { "build": "..." } }

3. 📝 Lock Files

All create lock files to ensure consistent dependency versions.

# npm: package-lock.json
# bun: bun.lockb
# deno: deno.lock

💡 The Big Picture

npm is the established standard 🏛️—best for teams working with existing Node.js infrastructure, enterprise projects requiring maximum compatibility, or when you need every npm package to work without issues. Choose npm when stability matters more than innovation.

bun is the speed-focused all-in-one ⚡—ideal for new projects where you want faster installs, built-in testing, and TypeScript without configuration. Best when you control your deployment environment and can adopt a newer runtime. Great for teams tired of managing multiple tools.

deno is the security-first modern runtime 🔐—perfect for APIs, scripts, and services where permission control matters. Choose Deno when you want web standards, built-in security, and don't need full npm compatibility. Best for greenfield projects with security requirements.

Final Thought: These tools aren't mutually exclusive—you can use npm for package management while evaluating bun or deno for specific use cases. For most existing projects, npm remains the safe choice. For new projects where you control the stack, bun offers the best developer experience, while deno provides the strongest security model.