What is a subdomain and how to set it up

A subdomain is a part of a domain name that is placed before the main domain and separated by a dot, for example: blog.example.com, where blog is the subdomain. It allows you to create separate sections of the website or independent projects within a single main domain, simplifying the structure and content management.

Main reasons for using subdomains in practice

Subdomains are used in practice for several main reasons:

1. Separation of functional areas of the site: for example, shop.example.com for a store; forum.example.com for a forum;
2. Organization of multilingual versions: for example, en.example.com, de.example.com;
3. Placement of testing environments for the site: for example, dev.example.com;
4. Creation of independent projects on one domain: for example, blog.example.com for a company blog;
5. Management of different departments or branches: for example, kyiv.example.com, lviv.example.com.

Difference between a main domain and subdomain

The difference between a main domain, subdomain and subdomains lies in their hierarchy, purpose and how search engines perceive them.

A main domain is the unique name of a site registered through a registrar. It consists of a name and domain zone (for example, example.com). This is the main address of the site used by users and search engines. Registering a main domain gives the right to create subdomains and manage the entire structure.

A subdomain is a third-level domain created based on the main domain. It is written in the format sub.example.com and can be used as a separate section of the site. Subdomains are created in the DNS management panel and do not require separate registration. Search engines consider a subdomain as an independent resource: it can be indexed separately, have its rating and backlinks.

Subdomains in the context of SEO and site structure

In the context of SEO, subdomains play a special role, as they are perceived by search engines as separate websites. This means that a subdomain like blog.example.com or shop.example.com will be indexed and ranked separately from the main domain example.com. This separation can be either beneficial or undesirable – depending on the project’s goals and the site’s structure.

Using subdomains is justified when it is necessary to separate functional areas of the site that differ in content and target audience. Large companies often allocate an online store, client cabinet, technical documentation or blog to subdomains. This allows for the creation of an independent structure, the application of separate SEO rules and, if necessary, the use of different platforms or management systems.

However, in terms of link equity and authority transfer, subdomains are not always suitable. Search engines do not treat them as part of the main site, so the backlink profile accumulated on the main domain does not automatically apply to the subdomain. This complicates promotion, since each subdomain requires separate work: creating links, filling with content and internal optimization.

The internal structure of the site becomes more complex when using subdomains. They do not participate in the internal linking of the main domain, do not inherit its metadata and are not always correctly interpreted by analytics tools without additional setup.

The choice between subdomains and subfolders depends on the project’s goals and the site’s structure. Subdomains, such as mail.google.com or support.microsoft.com, are used when there is a need to completely separate the functionality from the main resource – for web applications, support portals or individual services. If the task is to supplement the main site with a new section, such as a blog or reference information, it is better to choose subfolders, for example moz.com/blog or wikipedia.org/wiki/.

Step-by-step guide to creating a subdomain in ISPmanager

1. Log in to the control panel using the link provided by the hosting service and enter the administrator or user login and password.
2. In the main menu on the left, open the «WWW-domains» section, which lists all sites added to the system.
3. At the top of the interface, click the «Create» button to add a new domain.
4. In the «Name» field, enter the subdomain name in the format sub.example.com, where example.com is your main domain and sub is the desired subdomain name.
5. If you have several users in the system, select on whose behalf the subdomain will be created.
6. Specify the required IP address, usually the same as assigned to your main site.
7. In the «Root directory» field, specify the path where the subdomain files will be placed. Usually it is sub.example.com or a similar path inside /var/www/.
8. If necessary, enable SSL, select the PHP version, set up handlers or configure security settings.
9. Click «OK» or «Create» to complete the subdomain addition.
10. Make sure that the DNS zone of your main domain has an A record for the subdomain pointing to the correct IP address. If it does not exist, add it manually through the «DNS manager» section or in the registrar’s panel.

After completing all steps, the subdomain will be active and available for site loading or content placement.

Common mistakes when configuring subdomains and how to fix them

When configuring subdomains, mistakes often occur that lead to site inaccessibility, service malfunctions or content display issues. One common problem is specifying the wrong root directory. If a non-existent or shared directory with the main site is selected during subdomain creation, it can cause conflicts and loading of the wrong page. The solution is to set a separate, clearly defined folder for each subdomain.

When working with ISPmanager, all main settings are configured automatically when adding a subdomain. However, an error may occur if the subdomain was previously deleted manually but the files remain, or vice versa – if the directory is created, but the subdomain is not registered in the panel. It is important to ensure that the subdomain is displayed in the list of WWW-domains, correctly linked to the root directory and not duplicated in other settings.

Another frequent oversight is forgetting to enable the SSL certificate. If the main domain uses HTTPS, but the subdomain does not have a certificate, the browser will display a connection error. This can be resolved either by connecting a separate certificate or by using a wildcard certificate that covers all subdomains.

Another mistake is lack of indexing. If the subdomain is not added as a separate site in the CMS settings or the robots.txt file is not configured, it may be hidden from search engines. It is important to set the necessary rules and check site availability through the search console.

Finally, when moving or copying data to a subdomain, internal resource paths are often not checked. This causes errors in loading styles, images and scripts. It is recommended to adapt all internal links and ensure that the site displays correctly on the new subdomain.

FAQ

Are there limits on the number of subdomains that can be created?

Limits on the number of subdomains depend on the selected hosting plan. On QHost, most plans allow the creation of an unlimited number of subdomains.

Can a subdomain be used to redirect to another site or section?

Yes, a subdomain can be used to redirect to another site or a specific section. This is convenient for organizing traffic or separating business areas.

Is it necessary to register a subdomain?

Separate registration of a subdomain is not required. It is created in the hosting control panel based on an already registered main domain.