Wirebook › Glossary › Byte range
What is a byte range?
In one sentence: A numbered slice of a file, named by start and end byte, so a download can ask for only the missing piece.
A little more
A byte range names a slice of a file by start and end positions, counting from zero. The header Range: bytes=400000-599999 asks for that slice only. Servers that support ranges advertise Accept-Ranges: bytes.
Download managers and many browsers use ranges to resume after a drop, to fetch several slices in parallel, or to seek inside a video without downloading the whole file first.
It's a bit like… Asking the library for pages 40 to 59 of a book instead of the whole novel again.