CSV -> XLSX · Local tool
CSV to Excel
Turn a CSV into a real Excel .xlsx workbook, with zeros intact.
Last updated
How do I convert a CSV to an Excel file without Excel mangling it?
Drop the CSV onto filetity's converter and it writes a real .xlsx workbook in the browser tab, with nothing uploaded. The reason to do this rather than opening the CSV directly is what Excel does on import: it drops leading zeros from postcodes and account numbers, reads values like 3-4 as dates, and turns long identifiers into scientific notation, none of which can be undone once the file is saved. Here every cell is written as text unless you turn on number detection, and even then a value only becomes a number when the text survives the conversion exactly, so 42 becomes a number and 007123 stays as it is. The separator is detected from the header line, so a semicolon file from a European Excel converts properly instead of arriving as one column.
01 / Your device
the file stays here
02 / Browser memory
the work runs locally
03 / Back to you
saved on this device
When you would use this
Situations, not settings.
- A CSV Excel keeps ruining on import
- Postcodes losing their leading zero, order references turning into scientific notation, and 3-4 becoming a date. Writing the workbook first stops all three.
- Sending data to somebody who only opens spreadsheets
- A .xlsx opens with a double click and looks like a spreadsheet. A CSV opens in a text editor on half the machines you send it to.
- An export from a system that only writes CSV
- Convert once here rather than teaching everyone the import dialog's text-column setting.
How it works / no cloud
A conversion engine, not an upload form.
An .xlsx is a zip of XML parts, and filetity writes those parts in the page with the same zip library its Word and PowerPoint tools already use. Cells are written as text unless you ask otherwise, which is what keeps a leading zero and stops a long reference number turning into scientific notation on the way in.
- Offline ready
- Installable app
- No file limit queue
Straight answers
No accordion. Nothing hidden.
- Is it free?
- Yes, with no watermark and no page limit.
- Does it need an account?
- No. There is no account system.
- Is my file processed on my device?
- Yes. The file is read by your browser and never uploaded. There is no server to send it to.
- What formats are supported?
- CSV, TSV and semicolon or pipe separated text in. A real .xlsx workbook out, one sheet.
- What are the limits?
- Excel stops at 1,048,576 rows and 16,384 columns and the tool refuses above either before writing anything. Formatting, formulas and multiple sheets are not written.
- Does it work on mobile?
- Yes, on any modern mobile browser. Large files are limited by the memory the phone gives the browser.
- Does it work offline?
- Yes, once the page has loaded. The tool keeps working with no network connection.
- Why not just open the CSV in Excel directly?
- Because Excel changes it on the way in. It drops leading zeros from postcodes and account numbers, reads things like 3-4 as dates, and converts long identifiers to scientific notation, and none of that is reversible once saved. Writing the .xlsx first means the cells arrive as what they are.
- Can I get numbers I can actually sum?
- Yes, with the toggle. It only converts a value when the text survives the round trip exactly, so 42 becomes a number and 007123 does not, since turning that into 7123 loses information. Everything else stays text.
- Does it keep my semicolon separated file readable?
- Yes. The separator is detected from the header line and can be overridden, so a file written by a European Excel converts correctly rather than arriving as one giant column, which is what happens when it is opened directly on a machine with different regional settings.
- Are formulas or formatting carried over?
- No, and a CSV has none to carry: it holds text and nothing else. What you get is a clean workbook with your data in it, which you can then format in Excel. A value that starts with an equals sign is written as text rather than becoming a live formula.
- Will the file open in Google Sheets and Numbers?
- It is a standard Open XML workbook, so it should. It has been verified against LibreOffice, which reads and re-saves it correctly, and the format is the one every spreadsheet program documents support for. If yours refuses it, that is worth reporting.
Keep working locally
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