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FreeConvertter

CSV to XLSX Converter

Turn a CSV file into a proper Excel workbook — without losing leading zeros or garbling text.

CSVto

or drag and drop them here · up to 50 MB per file

Your files are processed on this device and never uploaded.

Instant conversion

There is no upload or server queue, so conversion starts the moment you drop a file and finishes as fast as your device can process it.

Your files stay private

Files are processed entirely inside your browser. They are never sent to, stored on, or seen by any server.

Nothing to install

Works on Windows, macOS, Linux, Android and iOS in any modern browser. No software, no extensions, no account.

How to convert CSV to XLSX

  1. 1

    Click "Choose CSV files" or drop your .csv files onto the converter.

  2. 2

    Optionally open "Options" to set the encoding, delimiter and how values are typed.

  3. 3

    Click "Convert" to build the workbook on your device.

  4. 4

    Click "Download" to save the .xlsx file.

Why convert CSV to XLSX?

  • Work in Excel safely — opening a CSV directly in Excel often strips leading zeros and misreads encodings; converting first avoids that.
  • Share a proper workbook — add formatting, formulas and charts afterwards.
  • One file for colleagues — XLSX opens the same way for everyone.

How the conversion works

The text encoding and delimiter are detected, the file is parsed as RFC 4180 CSV, and each value is typed conservatively: only values that are unambiguously numbers become numbers. The result is written as an XLSX workbook named after your file.

What is a CSV file?

CSV (comma-separated values) stores a single table as plain text: one row per line, with cells separated by commas (or semicolons or tabs in some regions). Cells that contain commas, quotes or line breaks are wrapped in double quotes.

CSV is the universal exchange format for data — almost every database, spreadsheet, CRM, bank and analytics tool can import and export it. It has no formatting, formulas or multiple sheets, and it does not record its own text encoding, which is why non-English CSV files sometimes open with garbled characters.

What is an XLSX file?

XLSX is Microsoft Excel’s default workbook format since 2007, based on the Office Open XML standard. A workbook can contain several sheets, each a grid of cells holding text, numbers, dates or formulas, together with formatting, charts and comments. Inside, it is a ZIP archive of XML files.

XLSX opens in Excel, Google Sheets, LibreOffice Calc, Apple Numbers and Hancom Cell. Files ending in .xlsm are the same format with macros enabled.

Frequently asked questions

Will zip codes, phone numbers and IDs lose their leading zeros?

No. Values like 007, phone numbers and IDs longer than 15 digits are kept as text exactly as written. Only plain numbers such as 42 or 3.14 become numbers. Choose "Keep everything as text" to keep every value as text.

My CSV came from Excel and Korean or other text is garbled. Will it work?

Yes. The encoding is detected automatically — UTF-8 as well as legacy encodings such as EUC-KR/CP949 used by Korean Excel, Shift_JIS, GB18030 and Windows-1251/1252.

My file uses semicolons or tabs. Is that supported?

Yes. The delimiter is detected automatically from the first lines, or you can choose comma, semicolon or tab yourself.

Are quoted values with commas or line breaks handled?

Yes. The file is parsed according to the CSV standard (RFC 4180), including quoted fields, doubled quotes and line breaks inside cells.

Is my file uploaded?

No. Everything happens in your browser.

Related guides

Why your CSV shows garbled characters in Excel (and how to fix it)When non-English text in a CSV turns into symbols like "é" in Excel, the file isn't broken — Excel guessed the wrong encoding. Here are three reliable fixes.Read guide →CSV vs XLSX — when to use whichBoth hold tables, but CSV is plain data while XLSX is an Excel workbook. The differences, when to choose each, and how to convert without damaging your data.Read guide →Excel removes leading zeros from your CSV — how to keep themZIP codes, phone numbers and IDs lose their leading zeros, and long numbers turn into 1.23E+19. Here's why Excel does it and how to keep your data intact.Read guide →

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