What Is Middleware in Web Development?
Middleware is code that runs between receiving a request and producing a response, able to inspect, modify, or reject the request/response, or pass it along...
Published October 7, 2026
Middleware is code that runs between receiving a request and producing a response, able to inspect, modify, or reject the request/response, or pass it along to the next step.
Why it exists
- Many concerns — authentication, logging, CORS headers, rate limiting — apply across many or all routes in an application
- Without middleware, that logic would need to be duplicated inside every individual route handler
How to apply it
- Middleware is typically chained — each one calls the next, forming a pipeline the request passes through in order
- Order matters — an authentication middleware, for example, must run before any middleware or handler that assumes the user is already identified
FAQ
Can middleware short-circuit a request?
Yes — a middleware can stop the chain early and return a response directly, such as an authentication middleware immediately returning a 401 without ever reaching the route handler.