CSV → JSON reads the first row as headers and turns every following row into an object with those headers as keys, honoring RFC 4180 quoting — a field containing a comma, quote or line break is wrapped in double quotes with embedded quotes doubled, so “Smith, Jane” stays one field. The delimiter is auto-detected: comma, semicolon (European Excel exports) or tab.
The size trade is dramatic and exact in direction: on the 7 tabular documents in our sample corpus (arrays of flat objects — users, orders, logs — converted with the same functions this page runs), pretty-printed JSON weighed 2.9× the CSV bytes (min 2.5×, max 3.8×), because JSON repeats every key on every row while CSV names each column once. The flip side: CSV has no types — true and 01234 are just characters until you coerce them.
“Only a header row was found — add at least one data row.” means the paste stopped after the column names. A one-column result from a many-column file means the delimiter went undetected — check for a semicolon or tab file whose first line contains commas inside quotes. Type coercion is on by default and deliberately conservative: clean numbers, true/false and null convert, but a leading-zero value like 01234 stays a string, because turning it into 1234 would corrupt it; switch coercion off to keep every cell a string.
Convert spreadsheet exports into API request bodies, test fixtures, NoSQL imports or JavaScript data structures — without the data touching a server.
This page is a focused view of theJSON ↔ CSV Converter, which has the full set of options.
With the coerce toggle on (the default), clean numeric cells, true/false and null convert to real JSON types — but deliberately not values with leading zeros, so postal code 01234 stays the string "01234". Turn coercion off to keep every cell a string.
Per RFC 4180, fields containing commas, quotes or line breaks are wrapped in double quotes, with inner quotes doubled. The parser honors that, so “Smith, Jane” stays one field.
Yes — the delimiter is auto-detected from the first line: comma, semicolon (common in European Excel locales) or tab all work.