A third-level domain is an independent site that is located on a second-level domain and is attached to it. That is, it is a subdomain of the main resource. Third-level domains are blogs and sites on free hosting, the name of which has this format: xxx.xxx.ru or xxx.xxx.com and others. The first word in this construction is the name that was invented by the user, and the second word after the dot is the domain of an older, second level. It has a subdomain. For example: poddomen.blogspot.com.
It should be remembered that when registering third-level resources on free hosting, the user does not receive absolutely any rights to them. In this situation, the owner is the owner of the main resource.
Owners of resources of the second level can make a younger resource - a domain of the third level, if there are no registrar restrictions on this operation. In the same way, domains of the fourth (xxx.xxx.xxx.org) and lower levels can be created. However, such a depth is rarely in demand.
A serious drawback is that the average third-level domain name is not very popular among the robots of some search engines. For some reason, subdomains are sometimes indexed by them very reluctantly and poorly maintained in the index. However, such problems do not always arise.
A third-level domain is most often used when it makes no sense for a new site to acquire an independent second-level resource. On a subdomain, it’s quite possible to place a selling page or a subscription page perfectly. That is, to make a website without cost on several pages. If you plan to build a large site on the basis of a subdomain, then you can install any CMS on it. Also, the owner of a second-level resource can, if desired, provide subdomains for creating blogs and sites. A lower-level resource can be used as offload for a crowded main site.
Before creating a third-level domain, you should first make sure that hosting has support for subdomains and the possibility of creating them is included in the cost of services. This information can be viewed in the hosting control panel. If the service is not provided, you need to request it from the host. It can be either paid or free. Each hosting has its own methods and capabilities for creating subdomains.
On some hosting sites, to create a simple site on a subdomain, it is enough to create another directory with a name like poddomen.yoursite.ru in the main folder in which the directory with the main site is located. When creating a subdomain, keep in mind that it must have an index.htm file or the site will not open. CMS systems are installed in the same way as on the main site, however, a separate MySQL database is required for the subdomain.
On some hosting sites, a third-level domain cannot be created by itself. To do this, you need to leave a request in your personal account indicating the desired name of the site of the 3rd level. Within a certain time, usually no more than a day, the administration will create the desired resource. After that, you need to enter the addresses of the DNS servers and fill the resource with information. For many hosters, the ability to create resources of lower levels was originally laid in the control panel, but on some servers the creation of third-level resources is generally prohibited. The way out of this situation may be the creation of subdirectories of the site.