Checks along the way
At a venue, visitors may pass through ticket and bag checks before entering. In a web app, middleware handles a browser request before the feature’s code runs and can adjust the response on its way back.
It might check who a user is, record activity, or translate data between APIs that use different formats.
Web middleware often runs on a server, either inside the app or in a separate service in front of it.
Why order matters
Middleware lets teams define common checks in one place. Several layers can make it hard to see where a request was changed or rejected. An access check must run before protected work. Teams keep each layer focused and make failures easy to trace.