Second-level domains

Top-level Internet domains like ".com" are shared by all the organisations in the domain. Second-level domain names like "yahoo.com" and "livinginternet.com" are registered by individuals and organisations.

Second-level domains are the addresses commonly used to host Internet applications like web hosting and email addressing.

Excluding the top-level domain portion, second-level domain names can have up to 61 characters. For many years, character were restricted to the 26 letters, 10 numbers, or the hyphen character, except the hyphen can't be the first or last character.

Under these conditions, there are 36 possibilities for the first and last character of the domain name, and 37 possibilities for the other 59 characters. Therefore, the total number of possible different second level domain names was:

37^59 x 36 x 36

=

433,018,769,429,481,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000

You can see why people say there will always be second-level domain names available. And since the introduction of internationalisation of the Internet domain name system, the number of possibilities for each character has increased considerably.

Thanks to the power of exponentiation, the number of different possible second level domain names is now so large as to be effectively infinite.

However, only a few Internet domains correspond to recognisable words, and the vast majority are random looking names.

If you have any questions about DNS then visit our DNS FAQ section for more help.