CSV to JSON

How do I convert a CSV file to JSON?

1. Open your CSV in a text editor or spreadsheet, copy everything including the header row, and paste it into the Input box.
2. Leave Delimiter on Detect automatically, or choose Comma, Semicolon or Tab if the guess is wrong.
3. Keep First row is a header ticked to get an array of objects; untick it for an array of arrays.
4. Tick Convert numbers and booleans so 42 and true come out as values rather than strings.
5. Choose the Indentation and click Convert to JSON.
6. Click Copy output, or Download to save a .json file.

The converter uses PapaParse, the most widely used CSV parser in the JavaScript world, so it copes with the awkward cases that break a naive split on commas: fields wrapped in double quotes, commas and line breaks inside those quotes, and doubled quotes used as escapes, all as described in RFC 4180. Windows (CRLF) and Unix (LF) line endings both work, and a trailing empty line is ignored rather than becoming an empty record.

With First row is a header ticked, each subsequent row becomes an object whose keys are the header cells, which is the shape most APIs, charting libraries and NoSQL databases expect. Untick it and you get an array of arrays, one inner array per row, which is better for a plain data grid or when the file has no header. Duplicate header names are kept as they are, so rename them in the sheet first if you need unique keys.

Convert numbers and booleans turns "42" into 42, "3.5" into 3.5 and "true" or "false" into booleans, leaving anything else as a string. Turn it off if you have values such as postcodes, phone numbers or product codes with leading zeros, because "00123" would otherwise become 123. Empty cells become empty strings either way.

Delimiter detection samples the first few lines and picks whichever of comma, semicolon or tab splits them most consistently. UK exports from Excel and Google Sheets are comma-separated; files from continental European Excel are usually semicolon-separated; copying cells straight from a spreadsheet gives tab-separated text, which also pastes fine. Everything runs as JavaScript in your browser tab, so customer lists and financial exports are never transmitted or stored. Files of a few hundred thousand rows convert in a couple of seconds.

How it works: this tool uses plain JavaScript running in your browser tab. No server is involved, so Kilnfile never sees your file. Last reviewed 20 September 2026.

Frequently asked questions