The plain-English version
Code that participates in a request pipeline before or after the main handler.
Why it matters
It can centralize repeated work such as request IDs, parsing, or authentication checks.
Let’s make it click
A request ID middleware attaches the same identifier to a response and associated server logs.
Vibe Bro’s heads-up
Ordering matters: a handler cannot rely on identity data before the relevant authentication step has run.
The docs behind it
Documentation links checked .
Editorial review · October 28, 2026
Supported: Express documents middleware in the request-response cycle and next/end behavior. Ordering and trust-boundary cautions are appropriate.