Bun is a fast all-in-one JavaScript runtime and toolkit: runtime, package manager, bundler, and test runner.
When to Use
Prefer Bun
for: new JS/TS projects, scripts where install/run speed matters, Vercel deployments with Bun runtime, and when you want a single toolchain (run + install + test + build).
Prefer Node
for: maximum ecosystem compatibility, legacy tooling that assumes Node, or when a dependency has known Bun issues.
Use when: adopting Bun, migrating from Node, writing or debugging Bun scripts/tests, or configuring Bun on Vercel or other platforms.
How It Works
Runtime
Drop-in Node-compatible runtime (built on JavaScriptCore, implemented in Zig).
Package manager
:
bun install
is significantly faster than npm/yarn. Lockfile is
bun.lock
(text) by default in current Bun; older versions used
bun.lockb
(binary).
Bundler
Built-in bundler and transpiler for apps and libraries.
Test runner
Built-in
bun test
with Jest-like API.
Migration from Node
Replace
node script.js
with
bun run script.js
or
bun script.js
. Run
bun install
in place of
npm install
; most packages work. Use
bun run
for npm scripts;
bun x
for npx-style one-off runs. Node built-ins are supported; prefer Bun APIs where they exist for better performance.
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Installs
1.6K
Repository
affaan-m/ecc
GitHub Stars
239.2K
First Seen
May 19, 2026
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