Every website address has a hierarchy—a specific structure that tells web browsers and search engines exactly where to find the content. This website’s domain is cobanker.com, but that’s just the start of the picture. Subdomains are often misunderstood tools that organize sites and make it possible to grow the site’s reach.
Simply put, a subdomain is a unique subdivision or completely separate section of a primary domain. If this site’s domain is cobanker.com, the www is the subdomain. Subdomains allow a business to organize different functions, applications, or geographies under one main site umbrella.
Understanding subdomains is crucial for segmenting website content and making informed decisions about site structure, particularly when considering Search Engine Optimization (SEO).
How a Subdomain Works
To understand a subdomain, you have to first know how a typical URL works. In a standard URL, the subdomain is always the leftmost element, often referred to as the “host.”
The format looks like this: [subdomain].[domain].[tld]
Common examples include blog.spotify.com, mail.google.com, or careers.microsoft.com. The most common default subdomain is www, though today’s best practices often advise using a more specific subdomain, like the ones listed here.
When organizing content on a website, the biggest decision involves choosing between a subdomain and a subfolder, or subdirectory. They look very similar to the casual observer, but they’re very different from a technical and SEO standpoint.
A subdomain often points to a completely different IP address, hosting environment, or server. IT’s treated as a separate, unique website by the DNS system. That makes it more ideal for highly segmented content or applications running on distinct technologies.
A subfolder is a file path or directory within the main website structure, existing on the same server and sharing the same root file system. It’s ideal for related content that should inherit the main domain’s authority. To go back to the previous Spotify example: spotify.com/blog/ would leverage a subfolder.
Why Businesses Use Subdomains
Subdomains have become more of a common practice in business websites, especially for larger, diverse companies with a range of different functionalities. There are some key reasons why they do this:
Separation of functionality: Many enterprise businesses use subdomains to isolate specialized features. For instance, a business that hosts its online store on an e-commerce solution like Shopify may use shop.brandname.com.
Testing and development: Subdomains are essential for safe development workflows. Developers often create staging or development environments (staging.website.com) that mirror the live site to support testing new features or updates without risking the stability of the public-facing domain.
Geographic or language targeting: International companies may use subdomains to better target specific audiences. For instance, a European division might use eu.company.com.
The most common application for small businesses is to set up an e-commerce shop.
SEO Considerations for Subdomains
Google is now much better at associating subdomains with the root domain, but it still requires a separate indexing process. As such, SEO experts debate whether subdomains or subfolders are better options. Ultimately, each may be better for different purposes.
One of the main considerations is link equity (or “link juice”), which refers to the authority and ranking power passed from one page to another via hyperlinks. When content is placed in a subfolder, inbound links and authority earned by the content directly contribute to the SEO strength of the main root domain. When it’s placed on a subdomain, search engines like Google may not immediately transfer its earned trust back to the root domain as efficiently as a subfolder, despite its improved efforts to do so.
The decision should be made based on technical needs first, and SEO consolidation second. Some key scenarios include:
Scenario
Recommendation
Rationale
Company blog/informational content
Subfolder (domain.com/blog)
Maximizes the transfer of earned authority to the main domain; consolidates all SEO value.
Separate function/application
Subdomain (app.domain.com)
Necessary for using different technology stacks, security requirements, or hosting environments.
Large-scale international sites
Subdomain (es.domain.com)
Clear geographic segmentation often preferred by larger international organizations.
How to Set Up a Subdomain
Creating a subdomain is a technical process managed through your domain registrar and hosting provider. To add a subdomain, you have to add specific records to the Domain Name System (DNS), which is the directory of the internet. This includes either:
An address record: This maps the subdomain (like shop) to a specific IP address where the content is hosted. This is the most common setup.
CNAME record: This maps the subdomain to another domain name. This is most common when you host your content on a third-party service and want to point your subdomain to their server using the domain name, not their IP address. You might do this if you’re building a store on Shopify or leveraging a tool like HubSpot as a CMS.
Once the DNS is pointed correctly, your hosting environment must be configured to recognize the new subdomain and direct its traffic to the correct folder or application location on the server.
FAQs
You can! It’s often called a “third-level subdomain.” For example, a development environment for a blog might be structured as dev.blog.example.com.
No, creating subdomains is typically free when you’re already paying for a root domain. You can usually create dozens or even hundreds of subdomains directly through your domain registrar or hosting account, though each may require its own separate hosting space.
The subdomain is logically and technically reliant on the primary domain. If you change your root domain from example.com to newbrand.com, then blog.example.com must also change to blog.newbrand.com.
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