JSON to CSV With Quoted Fields

The RFC 4180 rule for quoting is simple: enclose a field in double quotes if it contains the delimiter, a newline (CR or LF), or a double quote. If the field contains a double quote, double the quote inside the enclosure so "she said ""hello""" is the spec-correct way to represent the value she said "hello". Fields that contain none of those characters can be left bare without quoting, which keeps the file smaller and more readable.

Quote-when-needed is the more readable style and the default in FixTools. A CSV with mostly short alphanumeric values is much easier to scan when only the fields that genuinely need quoting are quoted. The file is also smaller, which matters at scale. The only downside is that some downstream consumers expect every field quoted and break on bare fields, though this is rare with modern tools.

Quote-all-fields is the heavier but more uniform style. Every field is enclosed in double quotes regardless of content. This produces larger files but eliminates any ambiguity for parsers that prefer a uniform structure. Some older ETL tools and certain regulatory data formats specify quote-all. If your consumer expects it, switch the mode in options.

Internal quote handling is the same in both modes. A double quote inside a value is doubled when the field is enclosed. Without doubling, the parser would interpret the internal quote as the end of the field. The doubling is the spec-mandated escape, and FixTools applies it consistently.