CSV to Excel
Build a genuine Excel workbook from CSV in your browser — no upload, and no encoding surprises.
Processed on your device — no upload
Paste a CSV or choose a file. A preview of the rows appears here before anything is written.
The workbook is assembled in your browser — an .xlsx file is a ZIP of XML documents, and both are built here. Text is written as UTF-8 throughout, so Arabic and accented characters open correctly rather than as mojibake.
How to use it
- Paste your CSV or choose a file.
- Name the file and the sheet.
- Download a real .xlsx workbook.
How it works
An .xlsx file is a ZIP archive containing a handful of XML documents: a content-type manifest, two relationship files, a workbook description and a sheet. Both the ZIP and the XML are assembled here, in your browser, which is why no spreadsheet library is downloaded and nothing is uploaded.
Text is written as inline strings and numbers as numeric cells. That distinction matters: a number written as text shows a green triangle in the corner of the cell and refuses to sum. Header cells stay text even when they look numeric, because a column named 2024 is a label rather than a value.
The real reason to use this rather than renaming a .csv is that everything CSV leaves ambiguous, .xlsx states explicitly. There is no delimiter to guess and no encoding to detect — the format declares UTF-8 internally, so Arabic, accented and Cyrillic text open correctly on every machine regardless of its locale.
Number detection is the same cautious rule used elsewhere on this site: values with leading zeros, plus signs or extra dots stay text, so phone numbers and identifiers survive.
A worked example
You have a customer export with Arabic names, and every time a colleague opens it in Excel the names appear as Ø£Øمد.
That is not a corrupted file. It is a correct UTF-8 file being read as if it were Windows-1256. Excel decides the encoding by guessing, and it guesses wrong unless the file starts with a byte-order mark.
Paste the CSV here and download the .xlsx instead. The names open correctly, on every machine, without anyone having to know what a byte-order mark is. The encoding is declared inside the format rather than inferred from the bytes.
The second recurring problem this solves: a European Excel expects semicolons and puts a comma-separated file into a single column. An .xlsx has no delimiter, so the question never arises.
One thing to check before sending. If the status line reports rows that do not have the expected column count, those rows will be written as they are — the CSV cleaner will show you which ones and pad them to fit.
To go the other way, Excel to CSV opens a workbook without needing Excel installed.
Questions
Why not just import the CSV into Excel directly?
Because Excel guesses at encoding and types on import, which is how Arabic turns to symbols and a leading zero disappears. Writing a real .xlsx settles both before the file is opened.
Is my data uploaded?
No. The workbook is assembled in your browser — both the ZIP container and the XML inside it — and nothing is transmitted.
Why not just rename my .csv to .xlsx?
Because they are entirely different formats. Excel would refuse to open it, or open it as text. This tool builds a genuine workbook.
Why does Arabic break when I open a CSV in Excel?
Excel guesses the encoding and guesses wrong without a byte-order mark. An .xlsx declares UTF-8 internally, so the problem disappears.
Will numbers be treated as numbers?
Yes. Numeric values are written as numeric cells so they sum and sort correctly. Values with leading zeros or plus signs stay text, since those are identifiers.
Can I create more than one sheet?
Not currently — one CSV becomes one sheet. Convert each file separately and combine them in Excel if you need a multi-sheet workbook.
Does it support formulas or formatting?
No. The output is plain data: values, correctly typed, with no styling, formulas or column widths.
Will it open in Google Sheets and LibreOffice?
Yes. The file follows the Office Open XML standard, which both read.
Is there a row limit?
Excel itself stops at 1,048,576 rows. In practice your browser memory will be the limit first, since the whole workbook is built in RAM.
Does this produce a real .xlsx file?
Yes — CSV to XLSX is what actually happens here. The output is a genuine Excel workbook with a sheet, typed cells and a header row, not a CSV renamed so Excel stops complaining.
Can I upload a CSV file to convert?
Yes — CSV file to Excel works the same as pasting the rows. Either way you get a real .xlsx workbook back, with typed cells and a header row, not a renamed CSV.