PDFs & Documents · Excel & CSV Converter
Convert Excel to CSV or JSON, and CSV to Excel, on your computer
Quick answer
Open Toolfox → Excel & CSV Converter, drop XLSX, XLSM, XLS or ODS spreadsheets to get CSV or JSON, or CSV and TSV files to get Excel, and click Convert. Convert the first sheet, a specific sheet or all sheets; when turning CSV into Excel, values like 007 stay text. It runs entirely on your computer (Mac, Windows or Linux). Files are never uploaded.
How to do it
- Open Excel & CSV Converter and drop spreadsheets or CSV files.
- Choose Convert to: Automatic, CSV, JSON or Excel (.xlsx).
- For workbooks, pick the first sheet, all sheets or a specific one, and the CSV delimiter.
- For CSV to Excel, keep or turn off the bold, filtered and frozen header row.
- Click Convert. report.xlsx becomes report.csv next to the original.
Options you can set
- Convert to
- Sheets
- Sheet name or number
- CSV delimiter
- Write dates as ISO 8601 (2024-03-31)
- Add a UTF-8 marker (helps old Excel open accented text)
- Bold header row
- Add filter buttons to the header
- Freeze the header row
Good to know
- Formulas are written as the values the spreadsheet app last calculated and saved; Toolfox doesn't recalculate them.
- Cell formatting (fonts, colors, currency symbols, percentages) isn't kept: numbers are written as plain values with Excel's 15-digit precision. Merged cells keep their value in the top-left cell.
- CSV → Excel: plain numbers like 42, -3.5 or 0.25 become numbers. Values with leading zeros (007), more than 15 digits, a leading +, thousands separators or exponents stay text, so IDs and phone numbers are never altered. Dates stay text.
- CSV files must be UTF-8 (in Excel, save as “CSV UTF-8”). If non-UTF-8 bytes turn up further in, the file is read as Windows-1252 (Western) and you'll be told.
- Password-protected workbooks and XLSB files aren't supported. Hidden sheets are included when converting all sheets.
Excel & CSV Converter FAQ
Are formulas kept?
No. Formulas are written as the values the spreadsheet app last calculated and saved; Toolfox doesn't recalculate them. Cell formatting isn't kept either.
Will 007 or long phone numbers be changed?
No. When converting CSV to Excel, values with leading zeros, more than 15 digits, a leading +, thousands separators or exponents stay text. Plain numbers like 42 become numbers.
Why do accented letters look wrong in my CSV in Excel?
Old versions of Excel need a marker to read UTF-8. Turn on “Add a UTF-8 marker” when converting to CSV.
Is Excel & CSV Converter in Toolfox free?
Yes. Excel & CSV Converter is one of 57 tools in Toolfox, a free app for Mac, Windows and Linux with no account, ads, limits or watermarks.
Does Excel & CSV Converter upload my files?
No. Toolfox processes files on your own computer and works offline; your files are never uploaded.
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Updated 2026-10-18 · Toolfox v0.2.1