, defined in RFC
3492, is a self-proclaimed "Bootstring encoding" of Unicode
strings into the limited character set supported by DNS
. The encoding is used as part of IDNA
, which is a system enabling the use of internationalized domain names in all languages supported by Unicode
, where the burden of translation lies entirely with the user application (e.g., web browser
For example, bücher becomes bcher-kva in Punycode, and therefore the domain name
bücher.ch would be represented as
xn--bcher-kva.ch in IDNA.
Punycode has been adopted by the national registrars of Germany, Austria and Switzerland starting on March 1st, 2004.