What happens when you convert CSV to XLSX
- Each line of the CSV becomes a row and each comma-separated value a cell. Numbers are stored as numbers, so they can be summed and sorted in the XLSX.
- The file is read by SheetJS running in your browser; nothing is uploaded.
How to convert CSV to XLSX online
- Press "Choose CSV files" and select one or more files, or drag them onto the box. You can add files of any size your device can hold in memory.
- There are no settings to choose: the converter keeps everything the target format can hold.
- Press "Convert to XLSX". The spreadsheet library, about 900 KB, loads the first time and then workbooks convert in a moment.
- Save each XLSX with its download button. Close the tab and every trace of the files is gone from memory.
Why convert CSV to XLSX?
CSV files usually come from data exports, imports into databases and exchanging tables between programs. People convert them to XLSX because XLSX is what Excel, Google Sheets and most business tools expect, and it keeps every sheet and formula.
In short, CSV is good at what it was made for, and XLSX is the more practical choice when the file has to open, upload or print somewhere else. CSV opens in every spreadsheet program and any text editor, while XLSX opens in Excel, Google Sheets, Numbers and LibreOffice Calc.
How to convert CSV to XLSX on Windows, Mac, iPhone and Android
On Windows
Open this page in Chrome, Edge or Firefox, drag your CSV files in from File Explorer, and press Convert. Each XLSX is saved to your Downloads folder.
On a Mac
Safari, Chrome and Firefox all work. Drag the CSV files from Finder onto the drop zone and the XLSX files land in Downloads.
On iPhone and iPad
Open the page in Safari and tap Choose CSV files. You can pick from Photos or from the Files app. The converted XLSX appears in Files, in the Downloads folder.
On Android
Open the page in Chrome, tap Choose CSV files and pick them from Files or your gallery. The XLSX is saved to the Download folder, where any file manager can find it.
Best settings for CSV to XLSX
There are no settings to choose: the CSV is read cell by cell and written as an Excel workbook with every sheet and its values and formulas.
Check the result in your spreadsheet program before deleting the original: formulas are carried over, but charts, images and styling are not, so a heavily formatted report will look plainer.
CSV vs XLSX: the differences
| CSV | XLSX | |
|---|---|---|
| Full name | Comma-separated values | Excel workbook |
| Type | spreadsheet | spreadsheet |
| Created by | no single author; standardised in RFC 4180 | Microsoft |
| First released | 1972 | 2007 |
| Compression | Lossless | Lossless |
| What it holds | one table of plain text values, one row per line | several sheets with values, formulas, formatting and charts |
| In a browser | opens in every spreadsheet program and any text editor | opens in Excel, Google Sheets, Numbers and LibreOffice Calc |
| Common uses | data exports, imports into databases and exchanging tables between programs | business spreadsheets, reports and anything shared with Excel users |
| MIME type | text/csv | application/vnd.openxmlformats-officedocument.spreadsheetml.sheet |
About CSV and XLSX files
What is a CSV file?
A CSV file holds a single table as plain text, with commas between values. It has no formatting, formulas or multiple sheets, which is exactly why every program can read it.
What is an XLSX file?
XLSX has been the default Excel format since Office 2007. Inside it is a ZIP archive of XML files, one per sheet, plus styles and shared text.
CSV to XLSX not working? Common problems
- The file will not open. Password-protected workbooks are encrypted, so they cannot be read without the password; remove the password in Excel first.
- Dates look like numbers. Spreadsheets store dates as numbers underneath; apply a date format to the column in your spreadsheet program.
- Special characters look wrong in Excel. The CSV is UTF-8; in older Excel, use Data, From Text/CSV and choose UTF-8 instead of double-clicking the file.
Convert CSV to XLSX from the command line
LibreOffice converts spreadsheets from the command line without opening a window:
soffice --headless --convert-to xlsx input.csvThe converter on this page does the same job in your browser, without installing anything.
CSV to XLSX converter FAQ
Will I lose quality converting CSV to XLSX?
Cell values and formulas are kept exactly. Charts, images and cell styling are not.
Why is the XLSX a different size from the CSV?
Workbook formats differ in how they compress, so the XLSX may be a little larger or smaller than the CSV.
Are my CSV files uploaded anywhere?
No. The conversion runs inside this browser tab using the open-source SheetJS library, so your files stay on your device. You can disconnect from the internet after the page and converter engine have loaded and it still works.
Can I convert several CSV files to XLSX at once?
Yes. Select or drop as many files as you like; they are converted one after another and each gets its own download button.
How do I open an XLSX file?
XLSX opens in Excel, Google Sheets, Numbers and LibreOffice Calc. XLSX is common for business spreadsheets, reports and anything shared with Excel users.
Is this CSV to XLSX converter free?
Yes. There is no sign-up, no watermark and no limit on how many files you convert. The site is paid for by advertising, and because conversions run on your device there is no server cost per file.
Can I convert CSV to XLSX on my phone?
Yes. The converter works in Safari on iPhone and iPad and in Chrome on Android. Converted files are saved to the Downloads folder.