Convert between JSON, YAML, and CSV. Everything runs locally in your browser using a small built-in parser for each format — it covers common block-style YAML and RFC 4180 CSV, but isn't a full spec implementation (flow-style YAML and multi-document files are best-effort). CSV conversion expects an array of flat objects, and since CSV has no way to represent a missing key versus an empty string, round-tripping through CSV can normalize missing fields to "".