HTTP headers / request header
User-Agent: ReqPad/1.1.2 (iPhone; iOS 19)
Identifies the client software making the request. Servers use it for logging, stats and occasionally (sigh) feature gating.
Some WAFs block requests with empty or "suspicious" User-Agents — if cURL works and your code does not, compare this header first.
The fastest way to see what User-Agent 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 · Authorization · Accept · Accept-Encoding · Accept-Language · If-None-Match · If-Match
Build the request, send it, read raw headers and timing — from your iPhone. Free to start.