JSON to CSV Converter

CSV (RFC 4180) is a table: a header row, then one line per record, with fields separated by a delimiter and quoted when they contain the delimiter, a quote or a line break. JSON has no such limit — objects nest and arrays hold any number of values — so converting means deciding how each nested value becomes a column. This converter walks every record, turns nested object keys into dot-notation names (customer.name, customer.address.city) and collects every key it sees, in first-seen order, as the header. A record missing a key gets an empty cell rather than shifting the columns.

Arrays have no single right answer, so there are three modes. Keep as JSON writes ["en","fr"] into one cell, which round-trips exactly. Join writes en; fr, which reads well in a spreadsheet but loses the difference between a string and a list. One column per index spreads the items over langs[0], langs[1] and so on, which suits short fixed-length arrays such as coordinates. To see the dot-notation keys a record produces before choosing, flatten one record first.

Excel on Windows guesses the text encoding of a CSV it opens, and guesses wrong for UTF-8 without a byte-order mark — é turns into é. Tick Add BOM for Excel and the downloaded file starts with U+FEFF, which Excel reads as a UTF-8 marker; Google Sheets and Numbers do not need it. Europe-based spreadsheets that use a comma as the decimal separator expect a semicolon as the delimiter, which the delimiter option provides.