An Internationalized Domain Nameⁱ (IDNⁱ) contains characters that may potentially be drawn from a repertoire of 96,000-characters, known as the Unicode repertoire. Prior to the availability of IDN, a domain name could only be displayed using a character set limited to the 26 letters of the basic Latin alphabet (a-z), the 10 digits (0-9), and the hyphen (-), thus limiting the number of languages that could be represented in native form. With IDN, a far larger number of languages may be displayed as their native speakers expect to see them in Internet applications (such as web browsers).

The form in which an IDN is recorded in the DNSⁱ is, however, still restricted to the initial letter-digit-hyphen (LDH) repertoire. Domain names in languages that require additional characters must
therefore be specially encoded if they are both to behave correctly in DNS transactions and be properly displayed. This encoding mechanism has been established by the IETFⁱ in a suite of protocols termed IDNA (Internationalized Domain Namesⁱ in Applications), specified in RFCs 3490, 3491, and 3492, with fundamental reference to RFC3454.