JSON to CSV

JSON stores data as nested objects and arrays, while CSV is a flat grid of rows and columns that Excel, Google Sheets and databases open directly. Converting between them means deciding how a tree fits into a table, and this converter does it with simple, predictable rules.

An array of objects becomes one row per object. The columns are every key found in any object, in the order they first appear, and a missing key leaves an empty cell. Nested objects become dotted column names, so {"address": {"city": "Paris"}} fills an address.city column. Lists of plain values are joined into one cell with "; " between them, and lists of objects are written into the cell as JSON text so no data is dropped. Turn flattening off to keep every nested value as JSON text instead.

Other shapes work too. An array of arrays becomes rows with no header, a list of plain values becomes a single value column, and an object that wraps one list of records, such as {"users": [...]}, uses that list. JSON Lines files, with one object per line, are read as well. The CSV is written with commas, quotes only where needed and Windows line endings, which every spreadsheet reads.