Internationalized Domain Names (IDN) include any domain with non-ASCII characters: Japanese ("日本語.jp"), Korean ("한국.kr"), emoji ("💩.la"). ICANN standardized IDN in 2003, and 152 character systems are usable as of 2024. Japanese .jp domains have been available since 2001 with about 220,000 registrations.
Internally, IDN converts to Punycode before traversing DNS. "日本語.jp" becomes "xn--wgv71a119e.jp", with browsers reversing the conversion for display. RFC 3492 defines Punycode using only ASCII letters and hyphens, letting IDN run on existing DNS infrastructure unchanged.
IDN homograph attacks are the central security challenge. Cyrillic "а" (U+0430) is visually identical to ASCII "a" (U+0061), so "аpple.com" can spoof "apple.com" in URL bars. Chrome, Firefox, and Safari implement IDN display heuristics that switch to Punycode for mixed-script or suspicious patterns, but pure single-script attacks (all Cyrillic) still render as Unicode. User education remains essential. For broader web know-how, related books are also available on Amazon.
Emoji domains ("I❤️.ws", "🍣.la") are supported by some ccTLDs (.la, .ws, .to). Major TLDs (.com, .net, .org, .jp) do not, so usage stays niche. Google treats IDN equivalently to Punycode for SEO, but copy-paste behavior and SNS link parsing varies, so always validate IDN short URLs across actual SNS and QR scans before promotion. ASCII ccTLDs (miji.be) remain the practical choice for short URL services, while IDN fits brand experiments.