Loading a spreadsheet into a database
Most import tools want CSV. Check that any identifier column with leading zeros survived, since that is the classic point where an export silently damages the data.
Use XLSX to CSV
Reads an Excel workbook in this tab and writes any sheet out as CSV. The file never leaves your device, which is the point for a spreadsheet.
Dates are read as dates, not serial numbersExcel stores a date as a count of days and marks it as a date only through its cell format. A reader that ignores formatting turns every date into a five-digit number. This one reads the format, and it keeps text like a leading-zero postcode as text rather than turning 0123 into 123.
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A spreadsheet is usually the last file anyone should hand to an unfamiliar website. Workbooks hold payroll, customer lists, pricing, patient records and half-finished financial models, and the conversion people want from them is trivially simple: pull one sheet out as comma-separated text. This tool does it entirely inside the browser tab. There is no upload, and this site has no endpoint that could receive one. Beyond privacy, two details separate a converter that produces usable output from one that quietly corrupts it, and both come down to the fact that a cell's displayed value and its stored value are different things. Getting that wrong is why so many exported CSVs arrive full of five-digit numbers where dates should be.
Work through the input
- An .xlsx file is a ZIP archive of XML parts, and the browser can read both natively, so the workbook is unpacked here without any large spreadsheet library being downloaded first.
- The workbook's own sheet list is read, so sheets appear under their real names and in the order they sit in the file rather than in whatever order the archive happens to store them.
- Cell values are resolved through the shared string table that Excel uses to avoid repeating text, and formula cells give up their cached result rather than the formula itself.
- Number formats are read from the styles, which is the only way to know a number is meant to be a date. Cells formatted as dates become readable dates; cells that merely contain numbers stay numbers.
- Fields are quoted only where they must be - when they contain the delimiter, a quote or a line break - and embedded quotes are doubled as the CSV convention requires.
When xlsx to csv is useful
A colleague's workbook with several tabs
Pick the sheet you need from the list and convert it. Repeat for the others; each becomes its own file, which is the only thing CSV can express.
Check the output
- Formatting is not data and does not survive. Colours, fonts, borders, column widths, conditional formatting and merged cells have no representation in CSV.
- Formulas are replaced by their last calculated value. If the workbook was saved without recalculating, that cached value is what you get.
- One sheet becomes one CSV, because the format has no concept of multiple sheets. Convert each in turn.
- Charts, images, pivot tables and macros are ignored entirely. CSV holds a grid of text and nothing else.
- Older .xls files, from Excel 2003 and before, use a completely different binary format and are not read. Open one in a spreadsheet application and save it as .xlsx first.
Questions about XLSX to CSV
Will my dates come out as numbers?
No. Excel stores a date as a count of days and marks it as a date only through the cell's number format, so this reads the formats. Cells formatted as dates convert to readable dates.
Do leading zeros survive?
Yes, when the cell holds text rather than a number. A postcode stored as text stays 0123. If the workbook stored it as a number, the zero was already lost before this tool saw the file.
Can I convert every sheet at once?
Not into one file, because CSV cannot represent more than one sheet. Choose each sheet in turn and download them separately.
Why is my .xls rejected?
The pre-2007 .xls format is a completely different binary structure, not a renamed .xlsx. Re-save it as .xlsx in any spreadsheet application first.
Is my spreadsheet uploaded anywhere?
No, and that is the reason this tool exists. Everything happens in the tab, which matters because workbooks routinely carry salary, customer and financial data.
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