HTTP headers / request & response
Content-Length: 348
The exact size of the body in bytes. Lets the receiver know when the message ends without closing the connection.
Mismatch with the actual body size causes hangs or truncation; with Transfer-Encoding: chunked it must be absent. 411 means the server insists on it.
The fastest way to see what Content-Length is actually doing is to send the request and read both sides raw — ReqPad shows auto-generated and custom headers for every request, on all six protocols, with history. Related references: status codes · Content-Type · Cache-Control · Connection · X-Request-Id
Build the request, send it, read raw headers and timing — from your iPhone. Free to start.