Punycode

Is a method of encoding that converts Unicode to ASCII. This is especially helpful when representing non-Latin or foreign characters that are used in Internet host names. Internationalized domain names (IDNs) are usually converted to Punycode. For example, the pretend site, bücher.co.uk, is transcoded in Punycode to xn--bcher-kva.co.uk. Here’s a breakdown of that output so we can explain each part:

• bcher-kva
  • This label is the transcoded form of bücher. It’s called a Letter-Digit-Hyphen (LDH) as such forms follow this syntax.
• xn--
  • This is called an ASCII Compatible Encoding (ACE) prefix, which is placed before the LDH. This is prepended by default to prevent confusing IDNs with hyphens from those that were converted to Punycode.
• .co.uk
  • This is the TLD of a domain name.

Related blog post(s):

• Out of character: Homograph attacks explained