Convert CSV to Excel (.xlsx)

No garbled text, and leading zeros, long numbers and date-like values go into Excel exactly as the CSV has them. The file never leaves your browser.

Your files stay safe — processed entirely in your browser. Nothing is uploaded.

Drop a CSV file here

or click to choose — CSV, TSV (tab-separated) or TXT

The file is read in your browser and never uploaded.

How to convert a CSV to Excel without losing anything

Double-click a CSV and Excel opens it, but not as written. Excel reads the text in its own guess of the encoding, so a UTF-8 file from a web service comes out garbled in Japanese Excel. And it converts values as it reads them: the leading 0 of a ZIP code or phone number disappears, a long ID number becomes 1.23457E+17 and loses its last digits, and values like 1-2 become dates. Microsoft documents the leading zeros and long numbers and suggests importing those columns as text.

This page does that for you. It reads the CSV in your browser, finds the columns Excel would change, and writes an Excel workbook (.xlsx) in which those columns are text. The file is never uploaded.

Drop the CSV

Drop a .csv (or a tab-separated .tsv or .txt) into the box above, or click to choose it. The encoding (UTF-8, Shift_JIS and others) and the delimiter are detected for you.

Check the preview

Each column is marked "Number" or "Text as is", and the columns Excel would have changed are listed with the reason. If the preview reads wrongly, change the encoding or the delimiter.

Save as Excel

Click "Save as Excel (.xlsx)". The workbook has the same name as the CSV. Open it in Excel: the header row is bold and frozen, with filters on it.

The CSV to Excel converter after reading a customer list: UTF-8 and comma detected, a green box listing the columns kept as text (customer number, ZIP code and phone for their leading 0, member number so it does not become 1.23E+17, registration date so it does not become a date, memo so it is not calculated), and a preview where only the amount column is marked Number. — Screenshot A made-up customer list in this converter. Every column Excel would change goes into the workbook as text; only the amounts become numbers.

Only columns where every value is a plain number become numbers, so they can be added up in Excel. Everything else goes in as text, exactly as the CSV has it.

How this converter works

An .xlsx file is a ZIP of XML files. This page writes those files itself, so the cell types are exactly what it chose, with no conversion on the way. Everything runs in your browser.

Reading the CSV: The encoding is guessed from the bytes (a BOM decides it when there is one), the same way as the mojibake fixer on this site. Quoted fields may contain commas, quotes and line breaks. The delimiter is the one (comma, tab or semicolon) that splits the first rows into the same number of fields.
Which values Excel would change: Numbers with a leading zero (00123, 090-…), numbers of 12 digits or more, values Excel reads as dates or times (1-2, 2026/10/01, 10:30), and values starting with =, +, - or @ that are not numbers. A column with any of these, or any other text, is written as text cells with the Text format, so editing a cell in Excel keeps it text.
Making the workbook: One sheet, named after the file. Column widths follow the content. The files are zipped with JSZip, which this site already uses for its ZIP downloads. JSZip license (MIT)

Limits

One CSV makes one sheet. Formulas, colors and merged cells cannot come from a CSV, so there are none. Files over 50 MB or 3 million cells are not taken. In a semicolon-separated file, where decimal points and thousands separators are written differently by region, only whole numbers become numbers.

Frequently asked questions

Is my file uploaded?

No. The CSV is read by a program running in your browser, and the .xlsx is made there too. Nothing is sent to this site or anywhere else.

Why does Excel drop the leading zeros of a CSV?

When Excel opens a CSV, it turns anything that looks like a number into a number, and a number has no leading zeros. It also shows numbers of 12 digits or more as 1.23E+17 and keeps only 15 significant digits. Microsoft describes this in "Keeping leading zeros and large numbers". Once the zeros are gone, changing the cell format afterwards does not bring them back.

Can I not do this in Excel itself?

You can. Microsoft's steps: import with Data > From Text/CSV, open the Power Query Editor (Transform Data), set each affected column's data type to Text and choose Replace current, then load. Newer Excel also has File > Options > Data > Automatic Data Conversion, where removing leading zeros can be turned off. This page finds the affected columns and does the same in one go.

Which columns become numbers?

A column becomes numbers only when every value in it (empty cells and lone dashes aside) is a plain number that Excel would show exactly as written: no leading zero, no trailing zero after a decimal point, at most 11 digits. Amounts written as 1,980 count, and that cell keeps its thousands separator. In a semicolon-separated file, only whole numbers count. Any other column, and every header, is text.

Is there a size limit?

Files up to 50 MB and 3 million cells. One Excel sheet holds at most 1,048,576 rows and 16,384 columns, and a cell at most 32,767 characters; a longer cell is cut there and the page says so.

How to Fix a Garbled CSV in Excel: Repair the File Right on This Page

A CSV opens in Excel as '譁�ｭ怜喧縺�' or '��'? Drop it into the box on this page and save it again as UTF-8 with BOM, which Excel reads correctly. The file is not uploaded. Also why it happens, and how to fix it with Excel's import or Notepad.