Accept-Ranges

The Accept-Ranges response HTTP header is a marker used by the server to advertise its support of partial requests. The value of this field indicates the unit that can be used to define a range.

In presence of an Accept-Ranges header, the browser may try to resume an interrupted download, rather than to start it from the start again.

<range-unit>

Defines the range unit the server supports. Though bytes is the only range unit formally defined by RFC 7233, additional range units may be registered in the HTTP Range Unit Registry. 

none

No range unit is supported, this makes the header equivalent of its own absence and is therefore rarely used, though some browsers, like IE9, it is used to disable or remove the pause buttons in the download manager.

Accept-Ranges: bytes

• If-Range
• Range
• IANA HTTP Range Unit Registry