What is a subdomain and how does it impact SEO?

Subdomains are subordinate sections of a domain. A domain basically consists of a domain name and a top-level domain (TLD):


Example: back2marektingschool.com

Domain name: Back2MarketingSchool

TLD: .com

A subdomain precedes the domain name and is used to subdivide websites.


-> de.back2marketingschool.com

In this case “de.” is the subdomain and could serve for the subdivision into the German language.

Besides subdomains, domain names, and top-level domains, URLs also have preceding transmission protocols (http or https).

The domain name is technically called a second-level domain. The next level of the hierarchy is the third-level domain, which is the subdomain. The ranking goes from right to left for URLs:

Top-Level: .com

Second-Level: domain name

Third-Level: Subdomain

what is a subdomain

Subdomains are used when the same hosting, IP address, and DNS settings are required.

Websites can be organized in subdomains or subdirectories:

de.back2marketingschool.com vs back2marketingschool.com/de/

Directories are located behind a slash (“/”).

The entire URL including all subdomains and directories builds the highest element, the root domain.

Email Subdomains

Subdomains do not necessarily have to be part of the website, but can also be email subdomains. Email domains have a similar structure:

@domain.tld -> @back2marketingschool.com

@subdomain.domain.tld -> @hi.back2marketingschool.com

What is an email subdomain in marketing

Subdomain Use Cases

Common use cases for subdomains are to differentiate into broad categories or logical separations that go out over subdirectories.

Login or member areas are a typical reason for third-level domains, as these are often managed separately from the website. For example, websites can be created using content management software (CMS) such as WordPress, but login areas can be managed separately.

Subdomains are often used when another system (other than the CMS) needs to access a website. Examples are marketing automation software like HubSpot or Marketo, content marketing solutions like Uberflip. As well as online stores.

Support areas can also be separated. This makes sense especially if other employees manage the content than the original website.

Career pages – which are also managed by an external system or other internal staff.

Career, login, and support subdomains also serve to easily separate the analytics such as for SEO Google Analytics reports.

Use cases


Example URL


Member area

Separate management


Online store

E-Commerce can also be carved out



Help section

Separate management and ticketing system



Separate management by HR and potentially external job board


Content Management

Management of content pieces like lead magnets



Blogging through 3rd party tools like HubSpot



Separate area for event organization and branding



Ongoing virtual webinar with its own dynamics


Landing Pages

Landing Page for performance marketing campaigns



Podcast marketing and hosting 


What are email subdomains used for? (Marketing examples)

Email subdomains are often implemented by 3rd party tools, such as Drift Email. They are often used for sending, measuring, and filtering. For example, automatic replies are filtered and categorized.

In that case, people who have left a company can be filtered out, but also additional information such as additional contacts or contact information can be crystallized. Please note that you must not email anyone without consent.

It can also be used to manage subgroups of subscribers. Let’s say you have an event and people have only agreed to event communication.

One of my favorite tactics is to use an email alias as a name. For instance, a newsletter can be sent from the CEO’s name. However, the email is actually sent from a subdomain, so it’s not the CEO’s real email.

Original CEO email address: f.lastname@brand.com

Subdomain email address: f.lastname@hi.brand.com

This usually goes unnoticed by the recipient and in truth, only digital marketing teams have access to the email inbox.

When is a subdomain useful?

Subdomains are useful when they need to cover different areas of a website like login areas or require another tool like marketing automation or content management solutions to host and distribute rich content pieces like podcasts, video series, or e-books.

Career pages can be excluded from marketing reports and allow for deflated SEO reports, for instance.

Most importantly, subdomains also serve as a safety net. Not every employee should be able to work on the main website. There is a risk for untrained colleagues to “crash” the site. When content is created on third-level domains, for example, this is often accompanied by third-party bogging such as HubSpot or separate access rights.

Subdomain SEO vs Subdirectory

Is blogging on a subdomain or in a subdirectory (blog.domain.com vs domain.com/blog) better for SEO performance? Google treats subdomains as separate entities in the search engine.

Therefore, positive SEO effects of a domain- and topical authority do not spill over to the primary domain when blogging on them. Normally, the domain gets topical relevance by publishing SEO-optimized blog posts.

However, this positive spillover effect only occurs when articles are published directly on the primary domain, in a subdirectory (e.g. /blog/), or categories (e.g. /SEO/).

Subdomain seo vs category

Subdirectories can also be linked to categories:

domain.com/blog/seo/ or


You can also create categories for subdomains:


You should therefore consider whether it makes more sense to blog through a third-party provider like HubSpot, and thereby take advantage of simplified reporting and additional marketing automation processes, or to achieve the best possible SEO result for the overall site.

In any case, it is not advisable to create a subdomain when blogging in the same environment/CMS as the main site. If the possibility of a subdirectory exists, this is always the better SEO choice. Google’s algorithms will increase the search results of your SEO efforts.