Convert between JSON and CSV

Without it, CSV → JSON keeps every cell as a string ("42" stays "42"). With it, strings that look like JSON values are converted: "42" → 42, "true" → true, "null" → null, "3.14" → 3.14. Useful for typed data, dangerous if you have IDs that happen to look like numbers but should stay strings ("00123" becomes 123).

JSON → CSV will JSON.stringify any nested object/array into the cell as text. CSV → JSON does not auto-parse cells that contain JSON — toggle "Coerce types" and the JSON values will be parsed.

The download includes a UTF-8 BOM so Excel opens it correctly with multi-byte characters. The clipboard copy does not include a BOM (Sheets and modern tools handle UTF-8 natively).

They get flattened, because a CSV row is a flat list of cells and there is nowhere for a nested structure to go. A key inside an object becomes a column named by its path — an address object with a city inside it turns into a column called address.city — and an array becomes either indexed columns or a single joined cell depending on what it holds. That is lossless enough to open in a spreadsheet and edit, and converting back reconstructs the nesting from the same paths. Where it stops being reversible is arrays of unlike objects: if the first item has three fields and the fifth has seven, the header was fixed by the first rows and the extra fields have nowhere to sit.

In locales where the decimal separator is "," (most of Europe), Excel uses ";" as its default CSV delimiter to avoid ambiguity. Files exported from a German or French Excel install will be semicolon-delimited.