Accept-RangesAccept-Ranges is a response header telling the client whether the server supports range requests (Range) for this resource. A value of bytes means the client can attempt partial fetches for resuming or seeking.
A value of none means range requests are not supported; even the header's absence is generally taken as no support.
It typically rides on a full 200 response or a HEAD response so the client can decide in advance whether to send Range: bytes=... requests. When the server advertises bytes, the client can parallel-download a large file in chunks, seek to a point in a video, or resume an interrupted download from the middle.
When a range request actually happens, the server responds with 206 Partial Content and Content-Range. Advertising support (Accept-Ranges) and actual partial delivery (206 + Content-Range) are two halves of the same flow.
Static file servers usually support bytes automatically, but dynamically generated responses or compressed streams often do not.
Accept-Ranges: <bytes|none>e.g. Accept-Ranges: bytes
bytes | Advertises support for byte-unit range requests. |
none | Explicitly states range requests are not supported (effectively like omitting it). |