CSV is text, not a spreadsheet: a record is a line, fields are separated by a delimiter and quoted fields may contain that delimiter or a newline. Understanding that model is most of the battle.
01A safe order of operations
View the data first: check the detected delimiter, the row and column counts and the per-column types.
Convert or transform one step at a time and re-check the result.
Profile or transpose only once you trust the parse, then download the result.
02Quote and encoding are the usual culprits
A file that opens wrongly is usually using a different delimiter, a different quote character or a non-UTF-8 encoding. Choose the input delimiter and encoding explicitly and the parse becomes predictable.
Frequently asked questions
Is my data uploaded?
No. Every file is read and transformed locally in your browser; nothing is sent to a server.
Does it open Excel files?
No. Paste or choose CSV/TSV/PSV text; binary spreadsheets are out of scope.
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