CSV to JSON converter
Convert data between CSV and JSON without handing your file to someone else's server.
Runs entirely in your browser. Nothing you paste is uploaded or stored.
Values with leading zeros stay text, so postcodes and IDs survive the trip.
What this tool does
It converts in both directions and tries to be right about the three things that break most converters: the delimiter, quoted fields, and type conversion.
The delimiter. A file exported from Excel in Germany, France or Russia is usually semicolon-separated. An export from an analytics tool is often tab-separated. Detection reads the first line and picks the most frequent candidate, and you can override it.
Quoted fields. A field wrapped in quotes may legally contain the delimiter itself, a line break, or an escaped quote written as two quotes in a row. A converter that splits on commas produces silent, plausible-looking garbage on exactly this kind of file.
Types. Numbers and true/false become real JSON types, which is what makes the output usable in code. Anything with a leading zero stays text, because a postcode or an order ID that loses its zero is corrupted data that nobody notices until much later.
When to use JSON to CSV
Mostly for people who have to look at data: an API response is not something a colleague can open in a spreadsheet. The converter builds the header from the union of all keys, so a partially filled dataset still produces a table with the right columns rather than shifted rows.
Nested objects and arrays are written into the cell as JSON text. A spreadsheet has no concept of nesting, and the honest options are to flatten with invented column names or to keep the value intact — this keeps it intact.
Questions
Why does my file use semicolons instead of commas?
Excel writes the delimiter its locale uses. In most of Europe the comma is the decimal separator, so Excel switches the column delimiter to a semicolon to avoid ambiguity. The tool detects this from the first line, and you can force any delimiter yourself.
What happens to values with a comma inside them?
Nothing, as long as they are quoted — which is what the CSV standard requires. The parser follows RFC 4180: a quoted field can contain the delimiter, line breaks, and doubled quotes to represent one literal quote.
Why did my postcode 01234 stay a string?
Because turning it into a number would delete the leading zero, which is a genuine data loss and one of the most common ways spreadsheets corrupt identifiers. Numeric conversion deliberately skips anything with a leading zero.
Can I convert JSON back to CSV?
Yes. An array of objects becomes a table where the header is the union of every key found, so rows with missing fields produce empty cells rather than shifted columns.
Is my data uploaded?
No. Parsing and conversion run entirely in your browser, which is the practical reason to use this rather than a server-side converter when the file contains customer data.