Media type / application
application/x-ndjson
Newline-delimited JSON: one complete JSON value per line, so a consumer can process a huge dataset without holding it all in memory.
Served inline: 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.
Browser behaviour
Downloads
Charset
charset ignored
Compression
Compress in transit
Send it like this
Content-Type: application/x-ndjsonThe format defines its own encoding, so no charset parameter is registered for this type. Sending one is harmless, but receivers are required to ignore it — it is not doing what people think it does.
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.
The format defines its own encoding, so no charset parameter is registered for this type. Sending one is harmless, but receivers are required to ignore it — it is not doing what people think it does.
The payload is text-like or otherwise repetitive, so gzip or Brotli removes real bytes. Enable it at the server or CDN.
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
application
Application
Subtype
x-ndjson
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
1 note- Unregistered, hence the x- prefix; application/jsonl and .jsonl are the other common spellings.
Response headers
Content-Type: application/x-ndjson
X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename="example.ndjson"
Vary: Accept-Encodingnosniff 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 {
application/x-ndjson ndjson jsonl;
}Apache
AddType application/x-ndjson .ndjson .jsonlCaddy
@type path *.ndjson *.jsonl
header @type Content-Type "application/x-ndjson"Extensions and other spellings
declaredFile extensions
Also written as
These reach the same handler in practice. Accept them on input; send application/x-ndjson on output.
File signature
No fixed signature — this format has no reliable magic number, so identify it by parsing rather than by the first few bytes.