HTTP headers / request header
X-Forwarded-Proto: https
Tells the origin which scheme the client actually used before TLS terminated at the load balancer.
Apps that build absolute URLs without honoring it generate http:// links behind HTTPS load balancers — the classic mixed-content factory.
The fastest way to see what X-Forwarded-Proto 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.