Convert Excel / CSV to JSON

How to use the converter

1. Drop an .xlsx, .xls or .csv file onto the drop zone. You can also try it right away with a sample.
2. Choose the sheet to convert. If the workbook has several sheets, choose "All sheets" to combine them into one JSON object keyed by sheet name.
3. Turn on Use first row as keys (header) to get an array of objects ("column title": value), or turn it off to get a two-dimensional array of rows.
4. Click Download .json or Copy to take the result.

Who it is for

• Front-end developers who need a product list, region codes or translation strings prepared in Excel as JSON for an app
• Planners and operators who need JSON for no-code tools, chatbot builders or automation services such as Zapier and Make
• People new to data analysis who want to see the structure of a public data CSV before working with it in JavaScript or Python

Conversion rules

• Empty cells: keys are kept and values are set to null, so every object has the same keys.
• Numbers and dates: number cells become JSON numbers, and date cells become Excel's internal serial numbers. If you need date strings, format the column as Text in Excel before converting.
• Duplicate column titles: repeated titles get suffixes such as _1 and _2 to avoid key collisions.
• CSV encoding: if UTF-8 fails, the file is read again as EUC-KR, so Korean keys and values are not garbled.

Why convert in the browser?

Business spreadsheets often mix in customer contacts, sales figures and prices that must not leave the company. Uploading the file to an online converter copies that data to a third-party server. This converter runs SheetJS directly in your browser, so the file is never sent anywhere, and you can use it even where company policy forbids external uploads.

Using the result

Converted JSON can be loaded in JavaScript with fetch('/data.json').then(r => r.json()), and becomes lists and dictionaries in Python with json.load(). You can also paste it into the JSON input of no-code tools, or use it as a request body in API tools such as Postman. Keys come straight from the first row, so rename the header row in Excel if you need English keys.

Tips for large data

Converting a sheet with hundreds of thousands of rows can produce a JSON string hundreds of megabytes in size. Keep only the columns you need in a separate sheet, or split the data into several CSV files. Because object keys repeat on every row, the two-dimensional array format with the header option off is much smaller.