We see country code top-level domains (ccTLD) for countries that exist, no longer exist, could exist, or only exist to some.

Country specific domain names are based upon the country’s ISO-3166 alpha-2 code (henceforth “country code”) and registration began in 1985 with the first being, unsurprisingly, .us for the United States of America. Since then most countries have a ccTLD in the Latin alphabet, with some also having an “Internationalised” version in other scripts e.g. Arabic, Chinese, Cyrillic.

The domain situation for countries without universal recognition is complicated, as one might expect with some having country codes, whereas others don’t. Taiwan has “TW” and the .tw domain, Palestine has “PS” and .ps, Northern Cyprus shares Turkey’s .tr but has no country code, and Kosovo, like Northern Cyprus, has no country code but has been allocated a temporary .xk domain since 1999. Should it become a recognised country in future and assigned a country code some options could be .ka, .ks, .kv, even .ko. However, the latter of .ko could be used in the event of a Korean reunification should that ever take place. The most obvious code isn’t always the correct one.

On the subject of communist states, we see traces of history in domains through the .cs (Czechoslovakia), .dd (East Germany), .su (Soviet Union), .yu (Yugoslavia) domains. Most of these are discontinued, but it turns out the .su domains are still active today even after the collapse of the USSR and SU was removed as a country code.

As in life, with destruction can come creation, and this is also true with domains - we saw the creation of .mk in 1993, and most recently South Sudan with .ss which was allocated in August 2011, one month after the country was recognised, and introduced in 2019 making it the youngest domain, and country at the time of writing.

The long answer: ISO 3166-1 alpha-2 and ISO 3166-1 alpha-3 define the two and three-letter codes for countries, respectively, but some unrecognised countries such as Kosovo have no such code. Because ISO-3166 reserves the “X” prefix for user-assigned codes it is often used where an alpha-2 or alpha-3 value is missing. Note that some “X” prefixed codes are in use by travel document specifications, where Kosovo uses UNK, and NATO.

Therefore, if you wish to define your own codes beyond those in the ISO specification, use an “X” prefix e.g. “XTP”.