Difference between Content-Range and Range headers?

Question

What is the difference between HTTP headers Content-Range and Range? When should each be used?

I am trying to stream an audio file from a particular byte offset. Should I use Content-Range or Range header?

Answer 1

Range is used in the request, to ask for a particular range (or ranges) of bytes. Content-Range is used in the response, to indicate which bytes the server is giving you (which may be different than the range you requested), as well as how long the entire content is (if known).

Answer 2

Actually, the accepted answer is not complete. Content-Range is not only used in responses. It is also legal in requests that provide an entity body.

For example, an HTTP PUT provides an entity body, it might provide only a portion of an entity. Thus the PUT request can include a Content-Range header indicating to the server where the partial entity body should be merged into the entity.

For example, let's first create and then append to a file using HTTP:

Request 1:

PUT /file HTTP/1.1
Host: server
Content-Length: 1

a

Request 2:

PUT /file HTTP/1.1
Host: server
Content-Range: bytes 1-2/*
Content-Length: 1

a

How, let's see the file's contents...

Request 3:

GET /file HTTP/1.1
Host: server

HTTP/1.1 200 OK
Content-Length: 2

aa

This allows random file access, both READING and WRITING over HTTP. I just wanted to clarify, as I was researching the use of Content-Range in a WebDAV client I am developing, so perhaps this expanded information will prove useful to somebody else.