Media type / video
video/x-flv
Flash Video, the container that carried web video before HTML5 — still the wire format for RTMP ingest into live-streaming services long after the player it was built for was retired.
Obsolete: No browser has played FLV since Flash was removed at the end of 2020. Serve MP4 or WebM instead; keep this type only for RTMP publishing and for identifying archive files.
Browser behaviour
Downloads
Charset
no charset
Compression
Already compressed
Send it like this
Content-Type: video/x-flvA binary payload has no character encoding. A charset parameter here is meaningless and occasionally confuses strict parsers.
Handling verdict
Browsers have no renderer for this, so it downloads even without a Content-Disposition header. That makes it the quiet default for anything you do not want opened in place.
A binary payload has no character encoding. A charset parameter here is meaningless and occasionally confuses strict parsers.
The format compresses internally. Another transport encoding costs CPU on both ends and typically changes the size by less than a percent — sometimes upward.
An `x-` prefix marks a type that was never registered. RFC 6838 discourages new ones, but several — like application/x-www-form-urlencoded — are now too widespread to change.
Anatomy of the name
RFC 6838Top-level type
video
Video
Subtype
x-flv
Registered in the unregistered tree.
Structured syntax
none
No suffix, so the payload format is defined entirely by the subtype itself.
Parameters
none
Beyond the charset rule above, this type defines no parameters of its own.
What trips people up
3 notes- Never registered with IANA, so the x- prefix is the type — there is no video/flv to graduate to.
- RTMP ingest to YouTube, Twitch, and most CDNs still speaks FLV on the wire even though nothing downstream serves it, which is why the type outlived its player.
- Sent inline it downloads rather than plays; there is no browser decoder left to hand it to.
Response headers
Content-Type: video/x-flv
X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename="example.flv"nosniff stops the browser second-guessing the type you declared, which is what makes the rest of this reliable. Content-Disposition: attachment names the saved file and removes any doubt about rendering.
Server configuration
extension mappingnginx
types {
video/x-flv flv;
}Apache
AddType video/x-flv .flvCaddy
@type path *.flv
header @type Content-Type "video/x-flv"Extensions and other spellings
with signatureFile extensions
Also written as
These reach the same handler in practice. Accept them on input; send video/x-flv on output.
File signature
46 4C 56 01
Check these bytes rather than the client-supplied Content-Type when validating an upload. The header is a claim; the signature is evidence.