CSV to Excel
Build a proper .xlsx workbook from one CSV file, or several at once.
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or drag them here
CSV or TSV · one sheet per file
Your file never leaves your browser during processing
How it works
To convert a CSV to Excel, drop the file onto this page and it is written as a real .xlsx workbook in your browser — with numbers and dates typed correctly, leading zeros preserved as text, and a frozen header row.
Renaming a .csv to .xls has been the folk remedy for this for twenty years, and it produces a file Excel complains about on every open. This page writes a genuine .xlsx instead: the same zip-of-XML package Excel itself produces, assembled in your browser from the rows in your CSV. Nothing is uploaded.
The interesting part of the conversion is not the container, it is the typing. A CSV is text all the way down, while a spreadsheet cell is a number, a date, a boolean, or text — and getting that wrong is what makes an imported file unusable. Numeric fields become real numbers so they can be summed, ISO dates become real dates so they can be sorted and filtered, and everything else stays text.
What is deliberately not converted matters just as much. Anything with a leading zero stays text, so zip codes, phone numbers, and product codes survive instead of losing their first digit — the single most common complaint about opening a CSV in Excel. Anything longer than fifteen digits also stays text, because past that a spreadsheet silently rounds; a credit card or IMEI number would come out altered. And ambiguous dates like 03/04/2024 stay text too, since there is no way to tell a British date from an American one without knowing who wrote the file.
Dropping several CSV files makes one workbook with one sheet per file, named after each file — which is the actual reason most people want an .xlsx rather than a CSV in the first place. Column widths are sized from the content, and the header row is bolded and frozen so it stays visible while scrolling.
FAQ
How do I stop Excel from destroying leading zeros?
This tool keeps them. Any field with a leading zero is written as text rather than a number, so 00123 stays 00123. That is a decision made when the file is built, which is why it works where opening the CSV directly in Excel does not.
Can I combine several CSV files into one Excel workbook?
Yes. Drop them all in and each becomes its own sheet, named after its file. That is the main thing an .xlsx can do that a CSV cannot.
Why are some of my dates still text?
Only unambiguous ISO dates (2024-03-04) are converted. A date written 03/04/2024 could be March or April depending on where it came from, and guessing wrong would silently move every date in the column by months.
What if my CSV uses semicolons or tabs?
The separator is auto-detected from the first line, and you can override it. Semicolon-separated files are standard in much of Europe, where the comma is the decimal mark.
Will the file open in Google Sheets and LibreOffice?
Yes. The output is standard OOXML — the same format Excel writes — so anything that reads .xlsx reads it.
Is my data uploaded?
No. The CSV is parsed and the workbook assembled entirely in your browser. The monitor under the tool shows zero bytes sent during processing.