CSV ↔ JSON Converter (RFC 4180 compliant)

Why RFC 4180 matters

CSV looks simple but has edge cases: a field containing a comma must be quoted; a field containing a quote must escape it as a doubled quote; a field can contain newlines if quoted. Naive split-on-comma parsers break on real-world data. This converter implements the RFC 4180 grammar exactly.

Naive parsers also break on Excel exports that use semicolons (common in European locales where ',' is decimal separator) or tabs (TSV). The delimiter dropdown handles all four common variants.

JSON shapes for output

Array of objects (default with header row): each row becomes {column: value}. The most common JSON shape, easy to consume in any language.

Array of arrays (header row off): each row becomes [v1, v2, ...]. Useful when columns aren't named or you want a positional structure.

Going JSON to CSV, the converter detects which shape you have. Objects: extracts unique keys across all rows for headers. Arrays: writes rows as-is.

Common pitfalls

Excel locale: in some European Excel installs, the default delimiter is ';' not ','. If your CSV looks like one giant column when imported, switch to ; in the delimiter dropdown.

BOM (Byte Order Mark): some Excel exports prefix the file with U+FEFF. We pass it through; if your downstream parser fails, strip the first 3 bytes.

Trailing newline: a CSV ending in '\n' adds an empty last row in some parsers; we filter empty rows automatically.

Numbers as strings: CSV has no types — '42' becomes the string "42" in JSON. If you need typed values, run a post-processing step that coerces known number columns.