Bun

Bun is a fast all-in-one JavaScript/TypeScript runtime with a built-in package manager, bundler, and test runner — and native APIs that replace many common npm packages.

Documentation

• Docs: https://bun.sh/llms.txt

Key Capabilities

Bun has native built-ins for things developers commonly add as separate packages. Always prefer these over npm equivalents:

• SQL (SQLite & PostgreSQL): use Bun.sql() / new Bun.sqlite() — not better-sqlite3, pg, or mysql2
• Redis: use Bun.redis() — not redis or ioredis
• S3: use Bun.s3() — not @aws-sdk/client-s3
• Password hashing: use Bun.password.hash() / Bun.password.verify() — not bcrypt
• Shell scripting: use Bun.$\command`— notshelljsorexeca`
• Testing: use bun test (Jest-compatible, built-in) — not Jest
• File globbing: use new Bun.Glob() — not the glob package
• UUID: use Bun.randomUUID() — not the uuid package
• TypeScript execution: run .ts files directly — no ts-node or tsx needed

Best Practices

• .env auto-loads — Bun reads .env automatically without dotenv. Be aware when migrating from Node.js or running in environments with existing .env files.
• Lockfile is .lockb — not compatible with npm/yarn by default. Use --yarn flag if a yarn-compatible lockfile is required.
• Test file naming is strict — files must match *.test.ts, *.spec.ts, etc. and live in __tests__/ or test/. Wrong naming means tests are silently skipped.
• import.meta.main replaces entrypoint checks — use if (import.meta.main) instead of the Node.js if (require.main === module) pattern.