Domain structure determines the hierarchy of a corporate website and how it can be expanded in the future. Once such decisions are made, subsequent adjustments often involve extensive migrations, so thinking them through before building the site is much easier than changing them after launch.
The Difference Between the Two
A first-level domain refers to the main domain, while a subdomain is a child domain extending under the main domain. A subdomain inherits the trust and authority already accumulated by the main domain, but as more levels are added, authority is diluted and maintenance becomes more complex. Once you understand this, many decisions become easier to make.
How to Allocate Them
The main domain hosts the brand's primary site, which is the default and most stable choice. Subdomains are suitable for businesses that are relatively independent from one another and need separate entry points, such as sites in different languages or independently operated product lines. If it is just a section within the site, there is no need to create a separate subdomain for it.
A Practical Principle
If something can be expressed with a path, try not to use a subdomain. Presenting an in-site section as a path makes unified maintenance easier than creating a separate subdomain, and it does not dilute authority. Only when content truly needs independent management and independent operation should you consider using a subdomain.
Certificate Issues with Multiple Subdomains
If you do need to create multiple subdomains, a single wildcard certificate can cover all subdomains under the same level, saving the trouble of applying for and renewing them one by one, and reducing the risk of interruption caused by certificate expiration.
Domain structure is not more professional simply because it is more complex. A design is appropriate if it keeps visitors from taking the wrong path and leaves room for future expansion.