JSON ⇄ CSV converter & JSON formatter
Paste or drop a file, then convert or format. Handles quoted CSV fields, embedded newlines, tabs/semicolons, and nested JSON objects.
🔒 Your files never leave your device
How it works
JSON → CSV takes an array of objects (or an object that wraps one), flattens nested objects into dotted column names like address.city, and writes arrays as JSON inside the cell. Columns are the union of all keys, in first-seen order.
CSV → JSON follows RFC 4180: quoted fields, doubled quotes, and line breaks inside quotes all work. Number detection skips values like ZIP codes with leading zeros and very long IDs, so they stay as text.
Very large files (tens of MB) may be slow, since everything happens in this tab.
Privacy: the tool runs in your browser, so nothing you add (files, text, passwords) is uploaded or stored by us. No account needed. It also works offline once loaded.