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File & Data Tools

Convert CSV to Excel

Get a real .xlsx file with auto-sized columns, without Excel mangling your data on the way in.

  • Free, no signup
  • No upload — runs on your device
  • No watermark
  • Unlimited use

CSV to Excel

Processed locally
Drop a CSV file here

Comma, semicolon or tab separated

Excel destroys data on import, and this is why the conversion matters

Open a CSV directly in Excel and it applies type inference to every cell. A postcode like 01234 loses its leading zero and becomes the number 1234. A product code like SEPT1 becomes the date 1 September. A long identifier like 1234567890123456 is rounded to fifteen significant figures and silently corrupted. Gene researchers renamed several genes because Excel kept converting them to dates.

None of this is recoverable — the original string is gone by the time you see the sheet. It happens on open, before you have a chance to intervene, unless you use the import wizard and explicitly mark every affected column as text.

Converting to .xlsx first sidesteps the whole problem. An xlsx cell has an explicit type stored alongside its value, so a cell written as the string 01234 stays the string 01234 when Excel opens the file. There is no inference step. This is the reliable way to hand a CSV to someone who will open it in Excel.

How it works

  1. Drop in a CSV file and check the preview
  2. Click Convert to Excel
  3. Open the .xlsx — leading zeros and codes are intact
Why nothing uploads. Every operation on this page happens inside your browser using JavaScript and WebAssembly. Your file is read into memory, processed, and offered back as a download. It is never transmitted. Disconnect from the internet after this page loads and the tool keeps working.

Frequently asked questions

Why does Excel remove leading zeros from my CSV?
Because opening a CSV triggers type inference on every cell, and 01234 looks like a number. Converting to .xlsx first stores each cell with an explicit type, so strings stay strings.
Will this stop Excel turning SEPT1 into a date?
Yes. Values are written as text cells with an explicit type. Excel reads the type rather than guessing from the content.
Are my column widths set automatically?
Yes, based on the longest value in the first 200 rows, capped at 40 characters so a single long cell does not produce an unusable column.
What if my CSV uses semicolons instead of commas?
The delimiter is detected automatically, which handles the European semicolon convention and tab-separated files without a setting.
How large a CSV can I convert?
Tens of megabytes comfortably. The whole file is held in memory, so a very large file is limited by your device rather than by the tool.

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