HEAD-NO-BODY

What it sends

A standard HEAD request. The server must respond with headers only — no message body.

HEAD / HTTP/1.1\r\n
Host: localhost:8080\r\n
\r\n

What the RFC says

“The HEAD method is identical to GET except that the server MUST NOT send content in the response.” – RFC 9110 Section 9.3.2

The server may include Content-Length or Transfer-Encoding headers to indicate what the body would have been for a GET request, but the actual response must contain zero body bytes.

Why it matters

If a server sends body content in response to HEAD, it corrupts connection state on persistent connections. A client or proxy reading the connection will interpret those extra bytes as the start of the next response, leading to response desync. This is a particularly dangerous defect in proxy environments where multiple clients share connections.

Sources

• RFC 9110 §9.3.2 – HEAD