CSV with tabs instead of commas, and the better choice more often than people realise. Tabs almost never appear inside a field, so the quoting rules that make CSV parsing miserable largely evaporate. Anything with prose, addresses or European decimals in it is safer as TSV.

Every conversion below runs in this page, on your own machine. Nothing is uploaded, there is no queue, and there is no account to make. Pick a target format, or just drop a TSV file above and choose afterwards.