Convert CSV to Excel (without the usual mangling)
The naive way to turn a CSV into an Excel file — open it in Excel, hit Save As — is exactly how ZIP codes lose their leading zeros, 16-digit order IDs get rounded to 15 significant digits, and anything that resembles a date gets rewritten into your locale’s format. Excel applies those conversions on open, before you’ve touched anything, and they’re baked in by the time you save.
This converter goes the safe route: it writes a real .xlsx workbook directly from the parsed CSV, cell by cell. Genuine numbers become numeric cells (so your sums still work); anything with a leading zero or more than 15 digits is written as text, which Excel then respects instead of “fixing”. The workbook is generated entirely in your browser and downloads instantly — your data never leaves the device.
Preset: the Excel export panel opens as soon as your file loads.
Drop a CSV, TSV or Excel file here
.csv · .tsv · .txt · .csv.gz · .xlsx — files up to 4 GB open here, in your browser. Nothing is uploaded; the file is read in place on your device.
Filters combine with AND. Use the search box for a quick any-column match. Regex filters use JavaScript syntax.
Untick to hide a column (hidden columns are left out of exports). Type to rename — renames apply to exports too.
Exports include your filters, sort, edits and cleanups. Hidden columns are left out; renamed headers apply. The file is generated on your device — nothing is sent anywhere.
How it works
- Drop the CSV (any delimiter — it’s auto-detected).
- Optionally filter, dedupe or fix cells first — the export reflects what you see.
- The Excel export panel is already open: set a sheet name if you like and hit Download.
- Open the .xlsx in Excel — ZIP codes, IDs and text look exactly like the source.
What “without mangling” concretely means
Three specific protections, all unit-tested against this site’s own export engine. Leading zeros: values like 02134 (a Boston ZIP) or 00501 (an IRS-famous one) are written as text cells — Excel shows 02134, not 2134. Long IDs: Excel stores numbers as 15-significant-digit floats, so a 16-digit credit-card-style ID pasted as a number ends in a wrong digit; here, anything past 15 digits stays text and survives exactly. Real numbers stay numbers: prices and quantities are written as numeric cells with the correct type, so SUM and pivot tables work immediately — this isn’t the everything-as-text cop-out.
Dates are deliberately conservative: date-looking strings are left as the text they were in the CSV rather than being guessed into Excel date serials. That’s the honest default — “03/04/2025” is March 4 in Boston and April 3 in London, and a converter that guesses is how gene names became dates in roughly a fifth of genomics supplementary files (a real, studied problem that got 27 human genes renamed in 2020).
Good to know
- The .xlsx export is capped at 100,000 rows — beyond that Excel is the wrong destination anyway (its grid ends at 1,048,576 rows); export CSV instead or split the file.
- Need Excel to read accented characters from a CSV instead? Use the CSV export’s “Excel-friendly (UTF-8 BOM)” option.
- The header row arrives bold with a frozen top row — small thing, saves a click every time.
Frequently asked questions
Why do leading zeros disappear when Excel opens a CSV?
Excel auto-detects cell types on open: 02134 looks numeric, and numbers don’t have leading zeros, so it becomes 2134 before you’ve touched the file. The only fixes are importing with columns forced to Text — or writing a real .xlsx where the cell type is already declared, which is what this converter does.
Will formulas or formatting be created?
No formulas — this is a data converter, not a spreadsheet builder. You get one sheet, a bold frozen header row, sensible column widths, numeric cells for numeric data and text cells for everything else. Formatting beyond that belongs in Excel itself.
My CSV has 500,000 rows — can I still get an Excel file?
Filter it down or split it first — the export here caps at 100,000 rows to keep workbook generation instant, and Excel itself becomes miserable long before its 1,048,576-row ceiling. For full-size data, CSV is the appropriate format.
Is anything uploaded during conversion?
No — the workbook is assembled in your browser (it’s a ZIP of XML parts, built locally byte by byte) and handed to you as a download. The Network tab stays silent throughout; it even works offline.