In the US you have relatively free rein when creating a domain name. Some technical requirements must, however, be met: You can use letters from A to Z, numbers from 0 to 9 as well as hyphens, although the hyphen cannot be placed at the beginning of the second level domain. Other symbols such as periods, slashes or question marks are not permitted. A domain name is generally expected to consist of up to 63 characters.
It could also be the case that some domain names, which could not be registered several years ago, are now possible to adopt. An example is a domain name with two characters such as www.hi.com.
Choose a name consistent with your website or business name and be aware that the domain name is not case sensitive. Avoid using 2 names together without a connector like “-“, otherwise you will risk your readability:
NiceShoes.online vs nice-shoes.online