Excel ↔ CSV ↔ JSON Converter

Convert between .xlsx, .csv, and .json — all in your browser.

Your files stay in this tab — nothing uploaded

Convert Excel, CSV and JSON files without uploading

🔒 Your files stay in this tab — nothing uploaded.

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Drag & drop or click — .xlsx, .csv, .tsv, .json

Output formatCSV delimiter First row is header

About this Excel/CSV/JSON converter

Drop an .xlsx, .csv, .tsv, or .json file (or paste CSV/JSON text) and convert it to any of the other formats. The Excel parser is hand-written with zero external libraries: it reads the ZIP structure of the .xlsx file using the browser’s DecompressionStream API, parses the XML worksheets and shared strings table with the native DOMParser, and builds a clean 2D array from the cell data.

This means your spreadsheet is never uploaded to a server — not even briefly. Every other Excel converter on the web sends your file to a backend for processing; this one does everything in your browser’s JavaScript. The tool previews the first 20 rows in a table before you export, and supports comma, tab, and semicolon delimiters for CSV output.

FAQ

Is my spreadsheet uploaded anywhere?

No. The file is opened and parsed by JavaScript running in your browser tab — it is never sent to a server, and there is no account or email gate before the download. You can disconnect from the internet after the page loads and the converter keeps working, which matters when the spreadsheet holds payroll, customer, or financial data.

Can it read .xls files (old Excel format)?

No. This tool reads .xlsx files only (the modern Office Open XML format used since Excel 2007). The legacy .xls format is a proprietary binary format that requires a much larger parser. Save as .xlsx in Excel first if you have a .xls file.

What happens with formulas in the Excel file?

The parser reads the cached (last-computed) result of each formula cell, not the formula itself. If a cell shows "42" in Excel because of a formula, this tool reads "42." Cells that were never calculated may appear empty.

Can it handle multiple sheets?

Currently it reads the first worksheet. Multi-sheet support (with a sheet selector) is planned for a future update.