CSV to Excel Converter

CSV to Excel Converter

Turn CSV files into a real XLSX workbook in your browser, with delimiter detection and no upload.

Drop CSV or TSV files here or choose files

One file or many, each becomes a sheet. Your data stays on this device, nothing is uploaded.

    How it works

    1. Add your CSV files. Drop one or several CSV or TSV files. Each one is read on your device and shown as a card with its detected delimiter, size and first five rows.
    2. Check the cards and options. Fix the delimiter if the guess is wrong, reorder or remove files, and choose header styling, text columns and column widths.
    3. Download the XLSX. The workbook is built in your browser, one sheet per file, and saved straight to your device. Nothing is uploaded.

    Questions, answered

    Are my files uploaded anywhere?

    No. CSV to Excel Converter runs entirely in your browser. Your files are read into memory on your device, parsed and turned into a workbook with JavaScript, and never sent to a server. You can disconnect from the internet and it keeps working.

    Why does my CSV open in one column in Excel, and how does this fix it?

    Excel guesses the separator from your system's regional settings, so a semicolon or tab separated file often lands in column A. This tool detects comma, semicolon, tab and pipe separators from the data itself (you can override it per file) and writes real columns into the XLSX, so there is nothing to guess when you open it.

    Will zip codes and long IDs keep their leading zeros?

    Yes, with "Keep text columns as text" on (the default). Any column where a value starts with a zero, such as 02134, or has more than 15 digits is stored as text, so it is not shortened or shown in scientific notation. Clean number columns are still stored as real numbers you can sum. Values that start with = are always stored as text, never as formulas.

    Can I merge several CSV files into one Excel workbook?

    Yes. Drop several files and each becomes its own sheet, named after the file (shortened to the 31 characters Excel allows and cleaned of characters like / and ?). Use the up and down buttons to set the sheet order. Files larger than Excel's 1,048,576 rows can be split across several sheets.

    Is it really free, and does it work offline?

    Yes to both. It is open source under the MIT license, with no account, no conversion limits, no file size caps and no ads. After your first visit the page is cached by a service worker, so it loads without a connection, and you can install it from your browser's menu as an app.

    Was this written by AI?

    Yes. CSV to Excel Converter was generated by Claude Code from a written specification inside an automated pipeline, with a test suite that runs in a real browser. The full source is on GitHub, so you can read every line before you trust it with your files.

    Built by one person, given away for free

    CSV to Excel Converter is a free alternative to paid tools like Convertio and Zamzar CSV to Excel. If it earns a place in your bookmarks, a coffee keeps the updates coming.

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