Paste or load your CSV, check the transposed preview showing rows as columns, then copy the result or download it as a new CSV file.
Usually when a report was written wide — one column per month or per metric — but the tool you are importing into expects one row per record. Transposing turns that wide layout into a tall one, or the other way round, in a single step.
The header becomes the first column of the output, so no labels are lost. Uneven rows are padded with empty cells first, which guarantees the transposed grid is rectangular and opens cleanly in any spreadsheet.
Transposing is done entirely in memory, so the limit is your device rather than a server. Very wide results are previewed with a column cap and a notice, while the downloaded file always contains every single cell.