Koa

Koa is a small web framework for Node.js built on async functions. It was created by the team behind Express and provides a minimal core with helpers for common server tasks.

Requests pass through a stack of middleware. Each function can do work before and after the rest of the stack runs, so control flows down and then back up. Error handling is simpler than with callback-based stacks because async functions return their results and errors directly.

• Async middleware that runs before and after handlers
• No middleware bundled in the core
• Helpers for content negotiation, caching and redirects
• Simple application object for building servers

Node.js developers who want a lean base and prefer to pick every middleware themselves. It suits custom API servers and teams that already write async code and want a clear, small layer between Node and their application logic.

Koa is open source under the MIT licence and free to use. It needs Node.js 18 or newer because it relies on modern async support. Since no middleware ships with it, plan to add packages for routing, body parsing and logging.