Wirebook › Glossary › Partial content
What is HTTP 206 Partial Content?
In one sentence: HTTP status 206: the server is sending only the byte range you asked for, not the whole file.
A little more
HTTP status 206 Partial Content means the server is answering a range request with only part of the resource. The Content-Range header says which bytes were sent and how big the whole file is.
If the server cannot or will not honour ranges, it usually falls back to 200 OK with the entire file. Clients that want to resume must then start over or switch strategy.
It's a bit like… A post office that delivers just the missing chapters of a magazine subscription, labelled with which pages they are.