For an emoji domain to work, it must be converted into so-called "Punycode". Punycode is a character encoding method used for internationalized domain names (IDNs). This representation is used when registering domains containing special characters. The ASCII representation starts with the prefix "xn--" and is followed by the emoji-containing domain name encoded as Punycode, for example "xn--i-7iq".
Each emoji has a unique Punycode representation. For example, "😉" in an IDN is represented as "xn--n28h". There are several generators on the Internet that allow one to convert emoji to Punycode and back.
Availability and registrationEdit
The availability of emoji domains is limited. As of May 2019[update], there are fourteen top-level domains for which registration is possible: .cf, .ga, .gq, .ml, .tk, .st, .fm, .to, .je, .gg, .kz, .com.kz, .org.kz, and .ws. 
The registration of an emoji domain can be more difficult than with normal domain names using only ASCII characters, since it is sometimes not possible to enter emoji into the online registration forms of domain name registrars, and instead the Punycode representation must be entered.
The first three emoji domains were created on April 19, 2001: ♨️.com (xn--j6h.com), ♨️.net (xn--j6h.net) and ☮️.com (xn--v4h.com). Cabel Sasser of Panic created 💩.la (xn--ls8h.la), "The World's First Emoji Domain", on April 13, 2011. In February 2015, Coca-Cola used a domain name containing a smiley emoji in an advertising campaign aimed at mobile users in Puerto Rico. A 2018 survey of the .ws TLD recorded approximately 25,000 registered emoji domains.
Another problem is that emojis can look different depending on the operating system, applications, and fonts used. Not all browsers support emoji domains. On Google Chrome and Firefox, emoji display as Punycode in the address bar. In Safari, on the other hand, emoji are visible in the address bar. Emoji domains are also visible in Google and Bing search results.
There are also issues with using emoji domains in social media. While they are well supported on Twitter and LinkedIn, Facebook and Instagram impose serious restrictions. Support varies on messaging platforms.
At present, only Punycode encoding is supported in e-mail domains, as in "email@example.com".
Emoji subdomains are like normal subdomains, except that they begin with emoji. Emoji subdomains are possible with many popular TLDs, including .com. As with any other emoji domain, emoji subdomains have to be converted into Punycode and can then be used as regular subdomains. Thus, domain combinations like 👍.website.tld (xn--yp8h.website.tld) are possible. This allows a wide scope of emoji domains outside of ccTLDs.
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