bun in practice

bun is not just a package manager: it is a full JavaScript runtime that aims to replace Node, npm, and several auxiliary tools (bundler, test runner) in a single binary written in Zig.

What bun does in a single tool

The result: fewer dependencies, less configuration, and execution speed often faster than Node.

Installing bun

On macOS and Linux:

$curl -fsSL https://bun.sh/install | bash

On Windows (PowerShell):

$powershell -c "irm bun.sh/install.ps1 | iex"

Via npm (alternative):

$npm install -g bun

Verify the installation:

$bun --version

Common commands

Install dependencies for an existing project:

$bun install

Add a package:

$bun add react

Add a devDependency:

$bun add -d typescript

Run a script:

$bun run dev

$bun dev

Execute a file directly (without node):

$bun run index.ts

Run tests:

$bun test

Run a one-off command:

$bunx create-next-app my-app

Remove a package:

$bun remove lodash

Why bun is so fast

bun is written in Zig, a low-level language with no garbage collector. It uses the JavaScriptCore engine (the engine behind Safari), known for fast startup. Its package installation is aggressively parallelized and uses its own binary cache format (bun.lockb).

On public benchmarks, bun installs dependencies 5 to 20 times faster than npm, and 2 to 5 times faster than pnpm.

The bun lockfile

bun generates a bun.lockb file (binary format, not human-readable). If you need to inspect the pinned versions, use:

$bun pm ls

Compatibility

bun is compatible with the npm ecosystem at ~95%. Most packages work without modification. Remaining edge cases: some native packages (.node bindings) and tools very specific to Node. In 2026, compatibility improves with every release.