What MIME type should I use for CSV?

RFC 7111

There is an RFC which covers it and says to use text/csv.

This RFC updates RFC 4180.

Excel

Recently I discovered an explicit mimetype for Excel application/vnd.ms-excel. It was registered with IANA in '96. Note the concerns raised about being at the mercy of the sender and having your machine violated.

Media Type: application/vnd.ms-excel Name Microsoft Excel (tm) Required parameters: None Optional parameters: name Encoding considerations: base64 preferred Security considerations: As with most application types this data is intended for interpretation by a program that understands the data on the recipient's system. Recipients need to understand that they are at the "mercy" of the sender, when receiving this type of data, since data will be executed on their system, and the security of their machines can be violated. OID { org-id ms-files(4) ms-excel (3) } Object type spreadsheet Comments This Media Type/OID is used to identify Microsoft Excel generically (i.e., independent of version, subtype, or platform format).

I wasn't aware that vendor extensions were allowed. Check out this answer to find out more - thanks starbeamrainbowlabs for the reference.

You should use "text/csv" according to RFC 4180.

Strange behavior with MS Excel: If i export to "text based, comma-separated format (csv)" this is the mime-type I get after uploading on my webserver:

[name] => data.csv
[type] => application/vnd.ms-excel

So Microsoft seems to be doing own things again, regardless of existing standards: https://en.wikipedia.org/wiki/Comma-separated_values

My users are allowed to upload CSV files and text/csv and application/csv did not appear by now. These are the ones identified through finfo():

text/plain
text/x-csv

And these are the ones transmitted through the browser:

text/plain
application/vnd.ms-excel
text/x-csv

The following types did not appear, but could:

application/csv
application/x-csv
text/csv
text/comma-separated-values
text/x-comma-separated-values
text/tab-separated-values

For anyone struggling with Google API mimeType for *.csv files, I have found the list of MIME types for google api docs files

Google Doc Format Conversion Format Corresponding MIME type Documents HTML text/html HTML (zipped) application/zip Plain text text/plain Rich text application/rtf Open Office doc application/vnd.oasis.opendocument.text PDF application/pdf MS Word document application/vnd.openxmlformats-officedocument.wordprocessingml.document EPUB application/epub+zip Spreadsheets MS Excel application/vnd.openxmlformats-officedocument.spreadsheetml.sheet Open Office sheet application/x-vnd.oasis.opendocument.spreadsheet PDF application/pdf CSV (first sheet only) text/csv TSV (first sheet only) text/tab-separated-values HTML (zipped) application/zip Drawings JPEG image/jpeg PNG image/png SVG image/svg+xml PDF application/pdf Presentations MS PowerPoint application/vnd.openxmlformats-officedocument.presentationml.presentation Open Office presentation application/vnd.oasis.opendocument.presentation PDF application/pdf Plain text text/plain Apps Scripts JSON application/vnd.google-apps.script+json

Source here: https://developers.google.com/drive/v3/web/manage-downloads#downloading_google_documents the table under: "Google Doc formats and supported export MIME types map to each other as follows"

There is also another list

MIME Type Description application/vnd.google-apps.audio application/vnd.google-apps.document Google Docs application/vnd.google-apps.drawing Google Drawing application/vnd.google-apps.file Google Drive file application/vnd.google-apps.folder Google Drive folder application/vnd.google-apps.form Google Forms application/vnd.google-apps.fusiontable Google Fusion Tables application/vnd.google-apps.map Google My Maps application/vnd.google-apps.photo application/vnd.google-apps.presentation Google Slides application/vnd.google-apps.script Google Apps Scripts application/vnd.google-apps.site Google Sites application/vnd.google-apps.spreadsheet Google Sheets application/vnd.google-apps.unknown application/vnd.google-apps.video application/vnd.google-apps.drive-sdk 3rd party shortcut

Source here: https://developers.google.com/drive/v3/web/mime-types

But the first one was more helpful for my use case.