CSV ↔ TSV ↔ Pipe Converter

Pastes data delimited one way and re-emits it delimited another. Auto-detects the input separator from the first line, parses with full quote / escape-quote support, and re-emits with RFC-4180-style quoting (cells containing the new delimiter, quotes, newlines, or edge whitespace are wrapped in "…" and inner quotes doubled). Useful when an Excel export hands you semicolons but your pipeline expects commas, or when you need TSV to paste cleanly into Google Sheets.

Quoting on output is the part that makes the conversion safe rather than merely different. A cell containing the new delimiter has to be wrapped or the row silently grows a column, and a cell containing a quote has to have it doubled or the parser on the other end loses the field boundary. Converting by find-and-replace skips both steps, which is why it appears to work until a single address with a comma in it shifts every column after it.

The semicolon export is not Excel being difficult. In locales where the comma is the decimal separator, a comma-delimited file would be ambiguous on every number, so Excel follows the system list separator and writes semicolons. The same spreadsheet therefore exports differently on two machines in different countries, and a pipeline that assumes commas breaks on one of them.

Tab-separated data is the format to reach for when pasting into a spreadsheet, because the paste path treats tabs as cell boundaries directly. It has a matching weakness: there is no way to represent a literal tab inside a field, so TSV is only safe when the data contains none. CSV can carry anything because it has an escape mechanism, which is exactly what TSV lacks.

Detection reads the first line, so a file whose header happens to contain a comma while the data uses semicolons is detected wrongly and parses into one column. Check the column count in the output before trusting a large paste; a conversion that produced one column is the signature of a misdetected separator rather than of malformed data.