HTTP headers / request header
Range: bytes=0-1023
Requests only part of a resource — download resume, video seeking. Success returns 206 with Content-Range; an impossible range returns 416.
A retry layer that stored a partial download may add Range automatically — the source of mysterious 206s.
The fastest way to see what Range 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.