CSV to Excel
The CSV to Excel tool creates a single-sheet .xlsx workbook with a bold header row. Numbers can be stored as real numbers so Excel can sum and sort them, or you can turn that off to keep every cell as text, which protects values such as phone numbers and codes with leading zeros.
The workbook has no formulas, charts, or formatting beyond the header; it is a clean container for your data.
Excel to CSV
Choose an .xlsx file and export one sheet, selected by name or position, or export every sheet as separate CSV files in a ZIP. Formulas are exported as their last saved values, and dates are written as YYYY-MM-DD so they are unambiguous.
Only .xlsx files are supported. Older .xls files and macro-enabled files should be saved as .xlsx first, and password-protected workbooks cannot be read.
Opening CSV correctly in spreadsheet apps
Spreadsheet programs may interpret CSV using your regional delimiter and may silently change values like long numbers or things that look like dates. When that matters, import the file as text with the correct delimiter, or convert it to .xlsx with number detection off.
All conversion happens in your browser tab and the files are not uploaded.