Add a subdomain to my DNS
DNS Subdomain
Understanding where a subdomain leads
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A DNS subdomain is not file that is automatically created in your hosting plan; it is a logical name, for example “blog.example.co.uk”, which can point to several destinations depending on your structure. It can lead to a specific folder, a separate website, an internal application, or to a service hosted on an external platform.
The DNS server ensures this link between the requested name and the technical destination. This role should not be confused with the DHCP, which assigns network addresses to devices on a local network. DNS subdomains are about publishing a name on the internet and linking it to a reachable resource.
Managing a DNS subdomain therefore involves linking a readable address to a unique arrival point or a specific resource. This resource can share the same hosting service as the main domain, or run on a separate infrastructure. This flexibility explains why subdomains are often used for public websites as well for technical services.
Managing a DNS subdomain therefore involves linking a readable address to a unique arrival point or a specific resource. This resource can share the same hosting service as the main domain, or run on a separate infrastructure. This flexibility explains why subdomains are often used for public websites as well for technical services.
Why structure your services with subdomains?
Why use subdomains
A subdomain separates different uses without adding extra domains, when the service has its own structure.
A well-organised DNS zone
A clear DNS zone identifies each function, limits errors and allows targeted delegation.
SEO and CDN strategy
Useful for SEO or CDN, provided the configuration, content and Google’s results are consistent.
Configure a subdomain in a DNS zone
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To make a DNS subdomain usable, you need to create the appropriate DNS record in the correct zone. An address record links the name to an IPv4 or IPv6 address, while an alias allows you to point the subdomain to another name that is already resolved. What you choose depends on the destination and on how it is expected to work on the web side.
The Time to Live indicates how long resolvers can keep a response before requesting more recent information. A short value can help during a change phase, while a longer value limits repeated requests when the configuration is stable.
In a multisite configuration, you add the subdomain in the hosting space, then you link it to the correct environment, be it a public website, application, target folder or dedicated instance. The same principle can appear in a zone file, with one line per name. Some headings remain in English in technical interfaces, but the rule remains simple: each entry must point to a specific and controlled destination.
In a multisite configuration, you add the subdomain in the hosting space, then you link it to the correct environment, be it a public website, application, target folder or dedicated instance. The same principle can appear in a zone file, with one line per name. Some headings remain in English in technical interfaces, but the rule remains simple: each entry must point to a specific and controlled destination.
What happens during DNS resolution
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When a person enters a subdomain address, their browser or system initiates a DNS resolution. The request generally goes to a recursive server, often provided by the network access or configured by the IT team. If this server does not already know the answer, it searches for the information from the DNS hierarchy.
The request can go back up to the root, then be directed to the servers of the relevant TLD. It then arrives at the authoritative DNS server. The primary server contains the zone data that indicates what response to give for the requested name. This chain explains why creating a subdomain is not limited to filling in a field in an interface. A hosting plan can make the operation clearer with forms and controls, but the technical process remains identical. The subdomain becomes reachable when the authoritative servers publish the correct information and the resolvers retrieve it.
The request can go back up to the root, then be directed to the servers of the relevant TLD. It then arrives at the authoritative DNS server. The primary server contains the zone data that indicates what response to give for the requested name. This chain explains why creating a subdomain is not limited to filling in a field in an interface. A hosting plan can make the operation clearer with forms and controls, but the technical process remains identical. The subdomain becomes reachable when the authoritative servers publish the correct information and the resolvers retrieve it.
A subdomain can isolate an editorial space, such as a magazine, documentation or a help centre. The content remains linked with the main domain, while having a separate structure for pages, templates and redirects.
Depending on your web architecture, this subdomain can point to a dedicated IP address, a content management system or a specific directory containing the published files. This separation helps the editorial team to carry out their work without modifying the corporate site.
An online shop can run on a subdomain in order to separate the path-to-purchase from the rest of the website. This approach is suitable when the sales part uses a different application, with its own security, payment and publication rules.
The subdomain can direct customers to an application server, a specific IP address or a specialised e-commerce service. You get to keep a clear web address, while managing a technical environment that is separate from the showcase site.
Business applications often use names like “app”, “admin” or “portal”. The label immediately indicates what the service does, which simplifies understanding for teams as well as for users.
On the DNS side, the entry directs requests to the relevant environment. This can be hosted separately from the public website, with its own update cycles, access rules, logs and monitoring controls.
Messaging services use dedicated records for sending, receiving and validating messages. Some subdomains are used to separate notifications, campaigns or transactional flows in order to avoid interference between uses.
Other technical services can use dedicated names for an API, static files or telemetry measurements. The subdomain then becomes a functional label, which is useful for managing day-to-day operations.
A pre-production environment or test environment benefits from having a subdomain that is functionally separate, even if it remains attached to the same domain. Teams test a version on a recognisable address, without directly exposing the changes to its main traffic.
This name can point to a separate instance, a temporary server or an isolated directory. However, remember to protect these spaces with authentication, access restriction and exclusion from indexing, to limit the risks of unwanted visibility in search engines, including Google.
A subdomain can isolate an editorial space, such as a magazine, documentation or a help centre. The content remains linked with the main domain, while having a separate structure for pages, templates and redirects.
Depending on your web architecture, this subdomain can point to a dedicated IP address, a content management system or a specific directory containing the published files. This separation helps the editorial team to carry out their work without modifying the corporate site.
Points to check before going into production
To facilitate control within the team, check the domain, TLD delegation, zone, record, publication, hosting, certificate and documentation before validation.
Check the domain and its delegation
Work in the authoritative DNS zone
Review each DNS registration
Distinguish between DNS and hosting
Frequently asked questions about DNS subdomains
What is the difference between a domain and a subdomain?
What is the difference between a domain and a subdomain?
A domain is the main name that you register, such as “example.com”. A subdomain adds a level to the left of this name, such as “blog.example.com” or “app.example.com”. It depends on the parent domain, but it can point to a different resource. This relationship allows you to create several identifiable spaces without registering a new domain name for each use. The domain carries the main identity, while the subdomain specifies a function, a service or an environment.
What is an FQDN?
What is an FQDN?
A fully qualified domain name (FDQN) refers to the complete name of a resource in the DNS hierarchy. In the example “www.shop.example.com”, “com” is the top-level domain (TLD), “example” is the domain, “shop” is the subdomain and “www” is an additional level. The full stop of the root is often implied in interfaces. An FQDN avoids ambiguity, as it describes the exact location of the name in the DNS tree.
Why does my subdomain not appear immediately after changing it?
Why does my subdomain not appear immediately after changing it?
The DNS cache can retain an old response for a duration linked to the zone settings and the resolvers used. When changes are made, some access points see the new destination quickly, while others continue temporarily to use the old information. This behaviour does not necessarily mean that the configuration is incorrect. To diagnose the situation, check the authoritative zone, then compare the responses obtained from several resolvers or networks.
How do you add a subdomain from a management interface?
How do you add a subdomain from a management interface?
To add a subdomain, open the DNS management interface associated with the relevant domain, then create the entry corresponding to the desired name. You then choose the type of record suited to the destination, such as an address or an alias. If the subdomain is for a website, also check the configuration on the hosting side so that the server recognises this name. You can check it works by reviewing the published entry and performing an access test.
Does a subdomain cost extra?
Does a subdomain cost extra?
A subdomain does not generally involve purchasing a new domain, as it is linked to a name that is already registered. Any potential cost comes instead from related services: separate hosting, specific certificates, application, traffic, storage or advanced options. Depending on the plan you have, DNS creation may be included or subject to certain limits. The right approach is to distinguish the name itself from the infrastructure that makes it work.
How do you compile a list of subdomains used?
How do you compile a list of subdomains used?
You can compile a list from the DNS zone, the hosting interface, SSL/TLS certificates, web logs and internal documentation. Each name must be linked to a function, a responsible person and a technical destination. This process uses the available information to identify active entries, abandoned services and names to be removed. An up-to-date inventory reduces oversights during migrations or audits.