The following is a list of rules of each registry. Please note that this list may not be a complete list and that each registry may adopt additional rules from time to time.

Domain Names have a variety of basic rules:

GENERAL EXTENSIONS

.COM - to be used for commercial and personal sites
.NET - recommended for companies involved in Internet infrastructure
.ORG - recommended for not-for-profit organizations
Use only letters, numbers, or hyphen ("-")
Cannot begin or end with a hyphen
Must have less than 63* characters, not including .COM, .NET and .ORG

* .com, .net and .org domain names exceeding a total of 26 characters are supported by most web browsers. However, certain web browsers, email programs and other Internet related applications may not support domain names over 26 characters.

.INFO - to be used for both commercial and personal sites
Use only letters, numbers, or hyphen ("-")
Cannot begin or end with a hyphen
Must have at least 3 characters and less than 63 characters, not including .INFO

.BIZ - sites restricted to commercial and bona fide business purposes
Use only letters, numbers, or hyphen ("-")
Cannot begin or end with a hyphen
Cannot have two hyphens in a row
Must have at least 3 characters and less than 63 characters, not including .BIZ

.NAME - to be used for personal sites
Must be composed of a first and last name (yourname1.yourname2.name)
First name (yourname1 in above example) must have at least 1 character and no more than 63 characters
Second name (yourname2 in above example) must have at least 3 characters and no more than 63 characters
Use only letters, numbers or hyphen ("-")
Cannot begin or end with a hyphen

.CC - Cocos (Keeling) Islands, to be used for commercial and personal sites
Use only letters, numbers, or hyphen ("-")
Cannot begin or end with a hyphen
Cannot contain all numbers
Must have at least 3 characters, but less than 47, not including .CC

.US - to be used by U.S. citizens and residents, U.S. corporations and other U.S. organizations and organizations with a presence within the United States
Use only letters, numbers, or hyphen ("-")
Domain names cannot begin or end with a hyphen
Domain names must be longer than 2 characters and cannot exceed 63 characters (this does not include the extension)

.WS - WebSite, to be used for commercial and personal sites
Use only letters, numbers, or hyphen ("-")
Cannot begin or end with a hyphen
.WS domains registered through Register.com must have as few as four and as many as 63 characters, not including the .WS extension