The plain-English version
Metadata sent with a request, separate from its address and body.
Why it matters
Headers can carry content information, authentication material, cache conditions, or request identifiers.
Let’s make it click
A JSON request declares its content type so the server knows how to interpret the body.
Vibe Bro’s heads-up
Avoid logging authentication headers or assuming that a header supplied by a client is trustworthy identity evidence.
The docs behind it
Documentation links checked .
Editorial review · October 28, 2026
Supported: MDN documents request metadata and content negotiation headers. The example does not treat a user-supplied identity header as authentication.