The word Subdomain is a very familiar term especially if you are in to webhosting business or a server administrator. But what is really meant by Subdomain and how is it different from any other domain? This brief article discusses about some important points of subdomains.

As the name suggests, subdomain is a part of a domain in the Domain Name System (DNS) hierarchy.  Before we get in to any further detail of subdomains, let’s see how DNS work, so we can clearly understand the concept of subdomain. Imagine a web URL in the following format: http://posts.sampledomain.com. In this URL, sampledomain.com is a subdomain of “com” top-level domain (TLD) and posts.sampledomain.com is a subdomain of sampledomain.com. According to the above example, we understand that subdomain as an entity with relative dependence rather than having an absolute dependence. How the DNS is structured can be considered same as directory structure of a file system but with a significant difference. When the directory hierarchy is written, it is written from left to right in a descending order. But domain hierarchy is written from right to left in descending order.

DNS is structured in such way that it can have 127 levels and each level can have 63 characters. But the total length of the domain name cannot be more than 255 characters. Obviously, no one is trying this out practically because the longer the domain name is, lesser people will visit the website. Sometime subdomains are called vanity domains when an ISP provides domains for each user in the format of alias.ispdomain.com. As an example, one ISP will provide subdomain for users such as http://john.ispdomain.com or http://jane.ispdomain.com. But term vanity domain has other uses as well.

In most of cases, subdomains are issued for different segments or departments of an organization or an institution. This is for easily identifying the domain names for respective departments so as to make web navigation easy. Sometimes, you can even have the hostname of the server that you host your web application as the domain name (Ex: testserver.maindomain.com).

Tags: Subdomain