OpenAPI Backend is a framework‑agnostic, TypeScript‑based middleware that lets you build, validate, route, secure and mock HTTP APIs directly from an OpenAPI 3.x definition. By registering handlers for operation IDs, security schemes, and validation hooks, it works with any Node.js server (Express, Fastify, Koa, etc.) and even serverless platforms, providing fast runtime routing and optional request/response validation without generating code. It’s aimed at backend developers who want to drive their API implementation straight from an OpenAPI spec.