express

Use when building APIs or web servers with Express.js — routing, middleware, error handling, or when working with the most widely-used Node.js HTTP framework. Also use when migrating Express apps or debugging Express-specific issues.

Model	Source
sonnet	pack: backend

Full Reference

┏━ 🔧 express ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓ ┃ Use when building APIs or web servers with Exp… ┃ ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛

Express.js

Express.js is the most widely-used Node.js HTTP framework. Express 5 (stable, default on npm since March 2025) auto-forwards rejected promises to error middleware — no more try/catch boilerplate in async routes.

Quick Reference

Item	Value
Current version	5.x (stable, latest on npm)
Min Node.js	v18+
Install	npm install express
TypeScript types	npm install -D @types/express
Key packages	helmet, cors, express-rate-limit, morgan, multer, compression
Docs	https://expressjs.com

Reference Index

I want to…	File
Set up a TypeScript Express project from scratch	reference/setup.md
Define routes, params, and nested routers	reference/routing.md
Add middleware (built-in and custom)	reference/middleware.md
Handle errors with custom error classes	reference/error-handling.md
Secure with helmet, CORS, rate limiting, and Zod	reference/security.md
Implement JWT, session, or OAuth authentication	reference/auth.md
Handle file uploads with multer	reference/file-uploads.md
Test routes with supertest	reference/testing.md
Optimize with compression, caching, and PM2	reference/performance.md
Migrate from Express 4 to Express 5	reference/migration.md

Usage: Read the reference file matching your current task from the index above. Each file is self-contained with code examples and inline gotchas.