206 Partial Content

The server is sending only the byte range(s) the client asked for with a Range header.

206 at a glance

Code: 206
Name: Partial Content
Class: 2xx Successful
Status: IANA-registered standard code
Defined in: RFC 9110, Section 15.3.7
Cacheable by default: Yes, heuristically cacheable (RFC 9110 section 15.1): without Cache-Control or Expires, caches may store it and pick a freshness lifetime themselves. Send explicit Cache-Control to stay in control.

What 206 means

206 Partial Content answers a Range request. The Content-Range header says which bytes are in the body and the full size. It powers video and audio seeking, resumable downloads and parallel download managers. Multiple ranges come back as multipart/byteranges. It is heuristically cacheable.

What typically causes a 206

Browsers seeking in <video> and <audio> elements.
curl -C -, wget -c and download managers resuming or splitting downloads.
PDF viewers fetching pages on demand.

Fix it on the server

Advertise support with Accept-Ranges: bytes. nginx and Apache handle static files automatically.
Compression and ranges interact badly: ranges apply to the encoded bytes, so many servers disable gzip for range requests.
Return 416 for ranges beyond the end of the file.

Fix it as a client or visitor

Send If-Range with the ETag when resuming so you do not stitch together two versions of a file.

Headers that go with 206

Header	Role
`Content-Range`	Bytes sent and total length, e.g. `bytes 0-1023/146515`.
`Accept-Ranges`	`bytes` if ranges are supported.
`Range`	Request header naming the wanted bytes.

Example response

HTTP/1.1 206 Partial Content
Content-Type: video/mp4
Content-Range: bytes 0-1048575/52428800
Content-Length: 1048576
Accept-Ranges: bytes