CSV → JSON Lines

You exported data as CSV from a spreadsheet or a database, and the tool on the other end wants JSONL: document database imports, ML training pipelines, BigQuery loads. Unlike a regular JSON array, JSONL puts one complete object on each line with no surrounding brackets — you can stream it, append to it, and merge files with a plain cat. Paste the CSV: the first line becomes the field names and every following line becomes one object.

The parser covers the essentials of RFC 4180: a quoted field may contain commas and line breaks, quotes inside a field are written doubled, and the \r from Windows files is ignored. Two behaviors worth knowing: every value comes out as text, with no type guessing — the 30 in an age column becomes the string '30' — and the separator is always a comma. Excel in many European and Brazilian locales exports CSV with semicolons; replace them first or everything lands in a single column.

Check the header line before converting: the names become JSON keys exactly as written, spaces and accents included — valid JSON, but awkward to access in code. A row with fewer columns than the header gets empty strings for the missing fields; extra cells beyond the header are dropped. The conversion runs in your browser with no upload, so a customer spreadsheet never leaves your machine.