CSV to XLSX converter
Turn a CSV file into a real Excel workbook with a worksheet you name.
Processed in your browser. This file is converted on your device and is never uploaded.
Converter
.csv up to 25 MB. You can also drag a file here.
No file selected.
About this tool
Opening a CSV in a spreadsheet application often means fighting an import dialog, and sending someone a CSV means hoping their software guesses the same separators you used. Converting to .xlsx removes both problems: the file opens directly and carries its own structure.
This tool parses your CSV in the browser and writes a real Excel workbook with a single worksheet that you name.
Supported formats and limits
- Input
- .csv
- Output
- .xlsx (application/vnd.openxmlformats-officedocument.spreadsheetml.sheet)
- Output name
- The original name with the new extension, for example data.csv becomes data.xlsx.
- File size limit
- 25 MB
- Processing
- In your browser. The file is not uploaded.
CSV against XLSX
| Feature | CSV | XLSX |
|---|---|---|
| Stored as | Plain text, readable in any editor | A ZIP of XML parts, needs software |
| What it can hold | Rows and columns | Rows and columns |
| Numbers stay numbers | No | Yes |
| Comments | No | Yes |
| Several in one file | No | Yes |
| Published | 1972 | 2007 |
How to use it
- Choose a .csv file, or switch to Paste text and paste the rows directly.
- Name the worksheet.
- Select Convert, then download the .xlsx workbook.
Limitations
- Every cell is written as text. Numbers and dates in your CSV will not become numeric or date cells, because interpreting them requires guessing a locale and a date order.
- The workbook has one worksheet. Producing several from one file is not supported.
- No formatting, column widths, formulas, or styling are applied.
- Worksheet names cannot contain : \ / ? * [ ] and are limited to 31 characters, which is an Excel restriction rather than one of this tool's.
- This tool expects comma separators. A semicolon-separated export will arrive as a single column.
Common problems
The file was refused before anything started.
CSV to XLSX converter checks the extension before it reads a byte, and it accepts .csv. Browsers report file types inconsistently enough that the extension is what decides.
Rename the file if the extension is simply wrong, or convert it to one of those first. A file whose extension does not match its contents is refused for the same reason, and that one needs converting rather than renaming.
It said the file was too large.
The limit here is 25 MB. It is not a policy but a measurement: everything runs on your own device, and past that size a phone runs out of memory rather than finishing slowly.
Split the file, reduce it before converting, or use a desktop program for that one. A machine with more memory will manage more, but the limit does not know which machine it is on.
I selected several files and only one converted.
This tool takes one file at a time. Doing several at once would multiply the memory in use, which is the thing most likely to fail on a phone.
Convert them one after another. Nothing is kept between them, so there is no state to reset.
Nothing happened for a long time on the first run.
CSV to XLSX converter downloads a library before it can begin, and it is fetched once and then reused. That wait is before the conversion rather than during it, which is why the progress bar sits still.
Leave the tab open and in the foreground; a background tab is throttled by the browser. Every conversion after the first one in a session skips this.
The tab reloaded itself part-way through.
The browser ran out of memory and restarted the page. At sizes approaching 25 MB this is the failure a phone hits first, and it looks like a crash rather than an error.
Try a smaller file, close other tabs, or run it on a computer. Nothing was uploaded or lost — the original file is untouched on your device.
The result opened in the wrong program.
The output is a .xlsx file, and your system opens that extension with whatever it was told to. Nothing about the conversion decides it.
Open it from inside the program you want, or change the default for .xlsx in your system settings. The file itself is correct.
Frequently asked questions
- Is my file uploaded?
- No. The conversion runs entirely in your browser. The file never leaves your device and no request carrying its contents is made.
- Why are my numbers stored as text?
- A CSV file carries no type information. Converting 007 to 7, or 03/04 to a date, changes the data. If you need numeric cells, select the column in Excel afterwards and convert it there, where you can confirm the result.
- Will the workbook open in other spreadsheet software?
- Yes. The output is a standard .xlsx file, which Excel, LibreOffice, Numbers, and Google Sheets all read.
- Can I add more worksheets?
- Not here. Convert each CSV separately and combine the workbooks in a spreadsheet application.
- Do I need to install anything or create an account to use CSV to XLSX converter?
- No, to all of it. CSV to XLSX converter runs inside the browser you already have, with no sign-up, no download, no watermark on the result, and no cap on how many files you convert. There is nothing to uninstall afterwards either, because nothing was installed.
- Does CSV to XLSX converter work offline?
- Once the page has loaded, yes. The conversion runs on your device, so it needs no connection to do the work. The first visit fetches the page and the code that does the converting; after that a lost connection stops nothing, and a converted file appears exactly as it would online.
- How large a file can CSV to XLSX converter handle?
- The limit is 25 MB. It is a deliberate one rather than a technical ceiling: the real constraint is memory, and a file that decodes to more than the device can hold fails in a way that is hard to explain. Phones run out well before laptops do, which is why the limit is set where it is.
- Can I convert several files at once with CSV to XLSX converter?
- Not here: this tool takes one file at a time, because what it does depends on choices you make about that particular file. Convert them one after another, or look at the batch converters in the same category, which are built for a folder at a time.