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. Options are Bytes or None.

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.

Specification https://wiki.gen.net.uk/doku.php/rfc:rfc7233