HTTP Developer’s Handbook

Range Requests

Range requests, sometimes referred to as byteserving, involve the Web client requesting specific pieces of a resource (specified as a range of bytes) rather than the entire resource. The Range header allows the HTTP client to request partial content, rather than the usual full content, by specifying a range of bytes it seeks to receive. The client should always be prepared to receive the entire content, because this is how a Web server handles an invalid range, and it is also how servers that do not understand the Range header will respond.

To request the first 500 bytes of content, a server can include the following Range header in the request:

Range: 0-499 

Ranges are represented using the hyphen character, and multiple ranges ...