Scarcity makes things valuable, and this is true in any field. As far as domain names are concerned, each suffix has only 36 single-letter prefixes, and many registries will give priority to reserving and protecting single-letter domain names. Even the oldest .com has only opened 3 single-letter domain names so far, namely Q.COM, X.COM, and Z.COM.

Let's take a look at the current status of these three domain names?

Q.COM, this domain name was once used by terminal Qwest to build a website, a company that provides a new generation of fiber optic network services. Later, Qwest merged with the US telecommunications operator CenturyTel, and the new company was renamed CenturyLink, and the domain name has been used to this day.

X.COM, was once used by Tesla CEO Musk to build a financial service platform. Later, X.com was used by PayPal, an online payment service provider that is highly sought after by hundreds of millions of users around the world. Until 2017, X.com was sold by PayPal, and Musk once again spent a lot of money to buy X.com back. Musk has now renamed Twitter to X and officially launched X.com as its official website.

Z.COM, the letter "Z" is the last of the 26 letters, so the domain name Z.com is also of great significance. The domain name is used by a network service provider called GMO Internet.