Turn an Excel workbook into CSV or JSON, or turn a CSV file into a real Excel spreadsheet. Pick the sheet and the separator you need, check a preview, and download. Your file is processed in your browser and never uploaded.
Processed entirely on your device. Nothing is uploaded.
An .xlsx file is a zipped package of XML files. This tool opens that package in your browser, reads the cell values from the sheet you choose, and writes them out as CSV or JSON. In the other direction it reads your CSV, works out the separator, and builds a proper .xlsx file with real numbers, a bold frozen header row and sensible column widths.
Because nothing is uploaded, it is safe to use for spreadsheets with customer lists, payroll exports or other private data.
| CSV | Excel (.xlsx) | |
|---|---|---|
| Contents | Plain text, one table | Several sheets, number types, column widths, styles |
| Opens in | Any program, database or script | Excel, Google Sheets, LibreOffice, Numbers |
| File size | Small | Larger, but compressed |
| Best for | Importing into other systems | Reading, sharing and editing by hand |
Comma-separated values are older than the personal computer. IBM’s Fortran compiler for OS/360 could read comma-separated data by the early 1970s, and the format spread because any program can read and write it. A common description of the format was only written down much later, in RFC 4180 in 2005.
Microsoft Excel first shipped in 1985 for the Macintosh. For two decades its files used a closed binary format. Excel 2007 switched to .xlsx, built on the Office Open XML standard that Ecma International published in 2006 and ISO adopted in 2008. Because .xlsx is a zip file of XML, tools like this one can read and write it without Excel installed.
How do I convert an Excel file to CSV? Choose Excel to CSV, select your .xlsx file, pick the sheet and separator, check the preview, and click Download CSV. The conversion happens in your browser.
How do I convert a CSV file to Excel? Choose CSV to Excel and select your file. The tool detects the separator, shows a preview, and creates an .xlsx file with numbers stored as numbers and an optional bold, frozen header row.
Why does my CSV show strange characters in Excel? Excel needs a UTF-8 marker at the start of the file to recognise accents and non-Latin letters. Leave the option for the UTF-8 marker switched on when you convert to CSV.
Why does my CSV use semicolons instead of commas? In countries where the comma is the decimal separator, spreadsheet programs write semicolons between columns. You can choose a comma, semicolon, tab or pipe as the separator when converting.
Will leading zeros be kept? Yes. When converting CSV to Excel, values such as 007 or 00123 stay as text so the zeros are not removed. Plain numbers such as 42 or 3.5 become real Excel numbers.
What happens to formulas and formatting? Formulas are exported as their last calculated value. Fonts, colours and number formats are not part of CSV or JSON, so only the values are kept.
Can I convert a workbook with several sheets? Yes. Pick one sheet at a time from the sheet list and download each one. A CSV file can only hold a single sheet.
Is there a file size limit? Files up to 30 MB are accepted. Very large sheets with hundreds of thousands of rows may be slow in a browser, so split them first if the page becomes unresponsive.