Convert internationalised domain names to and from Punycode (RFC 3492): bücher.example ⇄ xn--bcher-kva.example.

Punycode & IDN Converter. Operations: to-ascii — Encode each Unicode label as an xn-- label (one domain, email or URL per line; labels are NFC-normalised and lowercased). to-unicode — Decode each xn-- label back to Unicode (one domain, email or URL per line). encode — Encode one string with the bare RFC 3492 algorithm (no xn-- prefix, case kept). decode — Decode one bare Punycode string (no xn-- prefix) with the RFC 3492 algorithm.