Punycode (internationalized domain names)
Punycode (RFC 3492) is the encoding that lets internationalized domain names (IDNs) containing non-ASCII characters -- Cyrillic, Chinese, Arabic script, accented Latin letters -- work inside the DNS, which only ever transmits ASCII labels on the wire. An IDN label is converted to an ASCII-Compatible Encoding (ACE) form prefixed with xn--, so a label like café.example becomes xn--caf-dma.example internally, as specified by the IDNA2008 standard (RFC 5890-5894) governing which characters are valid. Browsers and other clients convert back and forth automatically, displaying the readable Unicode form while the DNS and WHOIS/RDAP records underneath use the xn-- form. The same mechanism is also a known phishing vector: visually similar characters from different scripts (homoglyphs) can form lookalike domains that render identically to a legitimate one. AdminKit's WHOIS tool resolves both the Unicode and xn-- forms of a domain when looking up registration data.
By AdminKit team, Netbase JSC · Updated