A domain name can contain the numbers 0-9, the letters a-z and the dash or hyphen character (“-”). It’s important to note that while domains can contain a hyphen, they can not begin or end with one. Additionally, the domain name system is not case sensitive, so you can register and write your domain name with both lowercase and uppercase letters.
Interchangeable upper and lower case letters is only true for the actual domain name. When spelling things out in a URL, the names of folders and files can be case-sensitive. In other words, http://www.igoldrush.com/introduction is different than http://www.igoldrush.com/Introduction depending on the web server.
Prior to December 1999, most domain names could only contain up to 26 characters including the extension. At that time, the current Registry for com/net/org domain names (InterNIC) increased the limitation to a total of 67 characters. This 67 character limit includes the “dot” and the TLD. So in the case of a “.com” name, for instance, you’ll be able to specify up to 63 characters yourself.
For the most common TLDs the minimum length of a domain name is 2 characters, although some lucky companies managed to register single character domains before that restriction was put in place (e.g. q.com was registered by Qwest). As of July 2009, there are a couple of Registries planning to offer single character domain names on auction basis. Stay tuned to our domain news section for any new developments.
Some top level domains from specific countries have additional limitations on length and on the number of characters in a domain. Some even specify a minimum length for a domain name of 3 characters or more. Be sure to check with your Registrar for the specific rules on your chosen TLD prior to registering your domain.
The system gets further complicated when using Internationalized Domain Names(IDNs). Do you remember how we said that a domain name can only consist of letters, numbers, and hyphens? Well, this isn’t entirely true when it comes to IDNs. What is true is that the Registry databases will only accept such characters. However, in cultures where people do not use the English alphabet, this could get confusing and remember, the whole purpose of the domain name system is to make remembering a website easier.
With IDNs, the non-English letters are translated into a set of English letters, then preceded by an ‘xn—’. So a domain spelled with Chinese characters would be translated to xn—longseriesofnumbers.com when stored in the Registry database. You can read more about IDNs here.
Did you know? You can include two consecutive hyphens in a domain name (“—”) in a domain name, except when the hyphens follow ‘xn’, which is reserved for IDNs. Although, you should consider that this will make it more difficult for people to remember your name and type it correctly into their browsers.
It’s time to move on and dispel some of the most common misconceptions about domain names.