Media type / text
text/csv
Comma-separated tabular data. The header parameter distinguishes files that carry a header row from those that do not.
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 required
Compression
Compress in transit
Send it like this
Content-Type: text/csv; charset=utf-8Send `; charset=utf-8`. Without it the receiver falls back to its own default — for some text types that default is us-ascii, and any non-ASCII character then renders wrong.
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.
Send `; charset=utf-8`. Without it the receiver falls back to its own default — for some text types that default is us-ascii, and any non-ASCII character then renders wrong.
The payload is text-like or otherwise repetitive, so gzip or Brotli removes real bytes. Enable it at the server or CDN.
Registered with IANA through a public review process, so the name is stable and every implementation can rely on it meaning the same thing.
Anatomy of the name
RFC 6838Top-level type
text
Text
Subtype
csv
Registered in the standards tree.
Structured syntax
none
No suffix, so the payload format is defined entirely by the subtype itself.
Parameters
header
Defined for this type in addition to any charset rule above.
What trips people up
2 notes- Spreadsheet software interprets leading =, +, -, and @ as formulas, so untrusted CSV is a code-execution vector on the recipient's machine.
- A UTF-8 byte order mark is what makes Excel open the file with the right encoding, despite being redundant in the standard.
Response headers
Content-Type: text/csv; charset=utf-8
X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename="example.csv"
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 {
text/csv csv;
}Apache
AddType text/csv .csv
AddCharset UTF-8 .csvCaddy
@type path *.csv
header @type Content-Type "text/csv; charset=utf-8"Extensions and other spellings
declaredFile extensions
File signature
No fixed signature — this format has no reliable magic number, so identify it by parsing rather than by the first few bytes.