Bun Setup and Comparison Guide | Generated by AI

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Question: What is Bun? How do you set a custom certificate and registry in Bun? How does it compare to npm?

Answer:

What is Bun?

Bun is an all-in-one JavaScript runtime + package manager + bundler + test runner written in Zig, built on JavaScriptCore (Safari’s engine) instead of V8. Key design goals: be fast by default, replace Node.js/npm/webpack/jest in one binary.

Core components in one binary:

Bun vs npm — Direct Comparison

Feature Bun npm
Written in Zig JavaScript/C++
JS Engine JavaScriptCore V8
Install speed ~10–25x faster (binary lockfile, parallel fetches) Baseline
Lockfile bun.lockb (binary) package-lock.json (JSON)
Workspace support Yes Yes
TypeScript Native, zero config Needs ts-node or compile step
.env loading Built-in Needs dotenv
Test runner Built-in (bun test, Jest-compatible) Needs Jest/Vitest
Bundler Built-in Needs webpack/esbuild/rollup
Node.js compat High (~95%) but not 100% 100% (it IS Node)
Maturity ~2023–2024 stable, still maturing Decade-old, battle-tested

Install speed comes from: binary lockfile (no JSON parse), hardlinks instead of copies, parallel HTTP/2 fetches, and Zig’s tight syscall usage.

Set Custom Registry

Global (all packages)

bun config set registry https://your-registry.example.com

Or edit ~/.bunfig.toml:

[install]
registry = "https://your-registry.example.com"

Scoped registry (e.g. @myorg)

In bunfig.toml (project or ~/.bunfig.toml):

[install.scopes]
"@myorg" = { registry = "https://npm.myorg.internal", token = "YOUR_TOKEN" }

With auth (npm-style token)

[install]
registry = "https://your-registry.example.com"

[install.registry]
token = "YOUR_NPM_TOKEN"
# or:
# username = "user"
# password = "pass"

Set Custom Certificate (SSL/TLS)

This is the pain point for corporate environments (e.g. your bank’s internal proxy with a self-signed CA).

Option 1 — caFile in bunfig.toml

[install]
caFile = "/path/to/your-ca-bundle.pem"

Option 2 — System trust store

Bun respects the system’s CA store on Linux/macOS. Add your cert to the system store:

# Ubuntu
sudo cp your-ca.crt /usr/local/share/ca-certificates/
sudo update-ca-certificates

# macOS
sudo security add-trusted-cert -d -r trustRoot -k /Library/Keychains/System.keychain your-ca.crt

Option 3 — NODE_EXTRA_CA_CERTS (Node compat env var)

export NODE_EXTRA_CA_CERTS=/path/to/ca-bundle.pem
bun install

Bun respects this env var for compatibility.

Option 4 — Disable TLS verification (dev only, never prod)

[install]
tlsRejectUnauthorized = false

Full bunfig.toml Example (corporate setup)

[install]
registry = "https://nexus.internal.bank.com/repository/npm-proxy/"
caFile = "/etc/ssl/certs/bank-internal-ca.pem"

[install.scopes]
"@bank-internal" = {
  registry = "https://nexus.internal.bank.com/repository/npm-private/",
  token = "YOUR_NEXUS_TOKEN"
}

npm equivalent cheatsheet

# npm                          → bun
npm install                    → bun install
npm install express            → bun add express
npm install -D vitest          → bun add -d vitest
npm run dev                    → bun dev  (or bun run dev)
npm config set registry <url>  → bun config set registry <url>
npx ts-node index.ts           → bun index.ts
npm test                       → bun test

Should you switch from npm to Bun?

Given your setup (AI CLI tools, Node scripts, bank proxy environments):

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