Excel to CSV / JSON

Excel to CSV or JSON

Spreadsheets arrive as .xlsx workbooks, but APIs, scripts and data pipelines want CSV or JSON. This tool opens a workbook, lets you pick a worksheet, and writes the table out in the format you need. Everything runs in your browser, so the file itself never leaves your device.

How to convert

1. Drop an .xlsx or .xlsm file onto the page, or click Upload file.
2. Choose the worksheet in the selector. Hidden sheets are marked and skipped by default.
3. Pick CSV or JSON.
4. For CSV, choose a delimiter and, if your data has non-ASCII text, turn on Add BOM so Excel reads the file as UTF-8.
5. For JSON, keep First row is headers on to get an array of objects; turn it off to get an array of arrays.
6. Copy the result or download it as your-file-sheet.csv / .json.

What is preserved

• Dates are stored in the file as numbers with a date format, so the tool reads the format and writes human dates such as 2023-03-15 or 2023-03-15 18:00:00, in both the 1900 and the 1904 date system.
• Numbers keep their original digits, so a cell holding 0.1 is written as 0.1 instead of a floating-point artefact. In JSON they become real numbers.
• Booleans become TRUE/FALSE in CSV and true/false in JSON, and error cells such as #DIV/0! are kept as text.
• Empty cells stay in place, so column alignment never shifts, and gaps left by the file are filled in.
• Text cells keep rich-text runs joined and drop phonetic annotations, and quotes, commas and line breaks are escaped following RFC 4180.
• Formulas contribute their last cached value, which is what Excel itself displays.

What is not supported

• Legacy .xls files and password-protected workbooks use a different container; save them as .xlsx first.
• Number formats are not re-created, so a percentage cell (0.15 with a 0.00% format) is written as 0.15, not 15%.
• Hidden rows and columns are exported like any other, so data that was filtered out still appears in the output.
• Styles, merged cells, charts and pivot tables are not part of the output.

Limits and privacy

Parsing, conversion and downloads happen entirely in your browser. Files up to 25 MB are accepted, and a worksheet is trimmed to the first 200,000 cells so the preview and the output stay responsive; the header note tells you when that happens.