206 Partial Content
Just the piece requested — the code that lets video skip to the middle.
The client asks for a slice with the Range header; the server answers 206 and delivers only those bytes, with Content-Range stating which piece came and how much exists in total.
It is the code that carries everyday life: dragging the video player's scrubber, resuming an interrupted download, fetching a file in parallel. Every time you jump to the middle of the movie, a 206 crosses the wire.
HTTP/1.1 206 Partial Content
Content-Range: bytes 1048576-2097151/31457280
Content-Length: 1048576
Content-Type: video/mp4