Excel ⇄ JSON / CSV Converter
Convert Excel files to JSON or CSV with sheet selection, and CSV or JSON data to Excel. Runs entirely in your browser; your files are never uploaded.
About the Excel to JSON and CSV converter
The TConverter Excel ⇄ JSON / CSV converter brings four spreadsheet conversions together on one page: Excel → JSON, Excel → CSV, CSV → Excel and JSON → Excel. It reads XLSX, XLS and ODS workbooks, lets you choose which sheet to convert, and writes new .xlsx files from CSV or JSON data. The tool is free, requires no sign-up, and runs entirely in your browser.
Spreadsheets are where a lot of business data lives, but applications and scripts usually want JSON or CSV. Typical uses include turning a product list maintained in Excel into JSON for a website, exporting one sheet of a workbook as CSV for an import tool, or going the other way and handing colleagues an Excel file built from an API response or a CSV export.
When you convert Excel to JSON, the first row of the sheet is used as the column headers and each following row becomes an object. Empty cells are kept as empty strings, so every object has the same keys. Dates are written as readable text in the form YYYY-MM-DD, or YYYY-MM-DD HH:MM:SS when a time is present, using your local time zone; this avoids the common problem of dates shifting by a day when they are converted to UTC. If a workbook has several sheets, you can pick one or choose All sheets to get a single JSON object keyed by sheet name. Excel → CSV works on one sheet at a time, since a CSV file can only hold a single table.
In the CSV → Excel mode, the delimiter (comma, semicolon or tab) is detected automatically and numbers are recognized, so files saved from Excel in different locales open correctly. The JSON → Excel mode uses the same rules as the JSON to Excel tool: it finds the main data array, flattens nested objects into dot-notation columns and leaves missing cells empty. For both modes you can select a file or paste the data and edit it before converting. Downloaded files keep the name of your original file with the new extension.
Files are processed locally with the SheetJS and PapaParse libraries and are never uploaded to a server. To keep the browser responsive, files larger than 25 MB are rejected when you select them, because the whole workbook has to be loaded into memory. If a file cannot be read, for example because it is damaged or not a real spreadsheet, a clear error message is shown.
Frequently asked questions
Which Excel formats are supported?
You can convert XLSX, XLS and ODS files to JSON or CSV. CSV and JSON data are converted to .xlsx.
What is the maximum file size?
Files up to 25 MB are accepted. Larger files are rejected in the browser because the whole workbook must be loaded into memory.
Can I convert all sheets of a workbook to JSON at once?
Yes. In Excel → JSON mode, choose All sheets when the workbook has more than one sheet. The result is a JSON object where each key is a sheet name and each value is that sheet's rows. CSV output is always one sheet.
How are dates in Excel converted to JSON?
Date cells are written as text in YYYY-MM-DD format, or YYYY-MM-DD HH:MM:SS when they include a time, based on your local time zone, so they do not shift by a day.
Are my spreadsheets uploaded to a server?
No. All conversions happen in your browser and your files never leave your device. The tool is free and does not require an account.