Punycode converter

Internationalised domain names (IDN) to ASCII Punycode and back, using the browser's native URL parser.

/tools/punycode converts between Unicode hostnames and their ASCII-compatible Punycode form (xn--…). Type münchen.de → xn--mnchen-3ya.de; type xn--bcher-kva.example → bücher.example. A toggle picks the direction.

Useful for setting up an IDN in DNS (which only takes ASCII), verifying that a suspicious link in an email is what it claims to be (homoglyph attacks: аpple.com with a Cyrillic а), or copying a non-ASCII domain into a config file that doesn’t speak UTF-8.

Uses the browser’s built-in URL / IDNA implementation — same algorithm Chrome and Firefox use for address-bar normalisation. No remote call.