Punycode

Punycode is a way to represent Unicode with the limited character subset of ASCII supported by the Domain Name System. For example "München" (German name for the city of Munich) would be encoded as "Mnchen-3ya".

Punycode is intended for the encoding of labels in the Internationalized Domain Names in Applications (IDNA) framework, such that these domain names may be represented in the ASCII character set allowed in the Domain Name System of the Internet. The encoding syntax is defined in IETF document RFC 3492.

The IDNA methodology encodes only select label components of domain names with a procedure called ToASCII. The procedure ToUnicode decodes the DNS label into Unicode representation.

In computing, Punycode is an instance of a general encoding syntax (Bootstring) by which a string of Unicode characters is transformed uniquely and reversibly into a smaller, restricted character set.

Encoding procedure

This section demonstrates the procedure for Punycode encoding, using the example of the string "bücher" (German for books), which is translated into the label "bcher-kva".