Originally, the domain part of a web address was all ASCII (so no accents, no emojis, no Chinese characters). This was extended a long time ago thanks to something called internationalized domain name (IDN).

Today, in theory, you can use any Unicode character you like as part of a domain name, including emojis. Whether that is wise is something else.

What does the standard says? Given a domain name, we should identify its labels. They are normally separated by dots (.) into labels: www.microsoft.com has three labels. But you may also use other Unicode characters as separators ( ., ．, 。, ｡). Each label is f