HTTP headers / request header
Referer: https://app.example.com/dashboard
The URL of the page that triggered the request (yes, misspelled in the spec since 1996). Used for analytics and (weak) hotlink protection.
Referrer-Policy can strip or trim it — never use it for security decisions.
The fastest way to see what Referer 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.