Just a quick post to share a tip I discovered this morning. I was generating a CSV file and for some reason when I went to open it in Excel, I got a message saying the file’s extension was CSV, but the file format was SYLK. Clicking through a couple message boxes opened the file up just fine anyway.

A bit of digging turned up the Wikipedia page linked above, and within it the format syntax description:

”’ID”’ record:
Use:
A header to identify spreadsheet type and creator.
Must be first record in the file.

Yep. If the first record of your CSV file is “ID”, Excel will attempt to intepret the file as SYLK. Changing “ID” to anything else (including “Id” or “id”) fixes the issue.