What is correct content-type for excel files? [duplicate]

I want excel files on a website to open in Excel when clicked, not get saved on desktop, or get opened embedded in a browser etc. Now obviously it all depends on how everything is configured for each user, but what's the best Content-Type and other settings to achieve just that most of the time?

For BIFF .xls files

application/vnd.ms-excel

For Excel2007 and above .xlsx files

application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

application/vnd.ms-excel

• vnd class / vendor specific
• http://en.wikipedia.org/wiki/Microsoft_Excel#File_formats

Do keep in mind that the file.getContentType could also output application/octet-stream instead of the required application/vnd.openxmlformats-officedocument.spreadsheetml.sheet when you try to upload the file that is already open.