How Do Subdomains Affect SEO?

In this article, we will explore the role of subdomains in SEO, weighing both the potential advantages and disadvantages. We’ll also provide insights into when it’s best to use a subdomain versus other options like subdirectories or separate domains.

What is a subdomain?

A subdomain is a part of a larger domain that operates as a separate entity while still being associated with the main domain. Structurally, it appears as a prefix to the primary domain name.

For example, in the URL blog.mypage.com, “blog” is the subdomain of “example.com.”

Subdomains can be used to organize different sections or functionalities of a website, such as:

• store.mypage.com for an e-commerce platform
• support.mypage.com for customer support
• blog.mypage.com for blog content

This structure allows webmasters to segment content or services while maintaining a relationship with the main domain.

Subdomains vs. subdirectories

Before diving into the SEO impact of subdomains, it’s essential to understand the distinction between subdomains and subdirectories. While subdomains operate as separate sections of a website, subdirectories (also known as subfolders) are simply extensions of the main domain and appear after the root domain in the URL.

For example:

• Subdomain: blog.mypage.com
• Subdirectory: example.com/mypage

Both approaches offer different advantages and disadvantages from an SEO perspective, and the decision of whether to use one over the other depends on the goals and structure of the website.

The impact of subdomains on SEO

The primary concern for SEOs is how subdomains influence website rankings and overall SEO performance.

So how can subdomains actually impact SEO?

1. Search engine indexing and crawling

Search engines like Google treat subdomains as separate entities from the primary domain. This means that when you create a subdomain, search engines must index and rank it independently from the main domain. Unlike subdirectories, which inherit much of the authority from the root domain, subdomains do not automatically benefit from the SEO authority of the main site.

For example:

If your website has a high domain authority, launching a subdomain (blog.mypage.com) may not immediately benefit from the ranking power of mypage.com. It needs to build its own authority over time through backlinks, content, and other SEO efforts.

However, Google has stated that its search engine algorithms are well-equipped to handle both subdomains and subdirectories. John Mueller, a webmaster trends analyst at Google, has clarified that Google doesn’t inherently favor one structure over the other. Therefore, as long as your subdomains are properly optimized and crawlable, they can perform well in search results.

2. Keyword targeting and relevance

Subdomains allow businesses to create distinct sections of a website for specific purposes, which can help target niche audiences and keywords. For example, a large corporation may create a subdomain specifically for its international audiences, like fr.mypage.com or de.mypage.com.

By using subdomains in this way, a site can target location-specific keywords and local search queries. The clear separation also allows for better targeting of content toward specific user intents without diluting the main domain’s SEO efforts.

However, because subdomains are treated separately, each subdomain must be optimized for SEO individually. This can create extra work for webmasters and SEOs, as each subdomain needs its own keyword research, content strategy, and on-page optimization.

3. Backlinks and domain authority

One of the most critical factors in SEO is the acquisition of backlinks (link building) from authoritative websites, which pass “link equity” or authority to the site.

The question arises: do subdomains benefit from backlinks earned by the main domain?

Because subdomains are treated as separate entities, backlinks directed to the main domain (mypage.com) typically do not contribute directly to the SEO authority of a subdomain (blog.mypage.com). Similarly, if the subdomain earns backlinks, the main domain may not receive the same benefit. This separation can make it harder to build and share authority across the entire website ecosystem.

That said, backlinks earned by subdomains are valuable in their own right and can help the subdomain rank well. Over time, if both the main domain and the subdomain are optimized and earning quality backlinks, the overall brand may benefit from increased visibility, even if the technical SEO benefits are segmented.

4. Content duplication risks

When a website uses both subdomains and subdirectories, or when content is spread across multiple subdomains, there is a potential risk of content duplication.

For example, if similar content appears on both blog.mypage.com and mypage.com/blog, search engines may have difficulty determining which version is the original or most authoritative.

Google and other search engines penalize sites for duplicate content because it can confuse search engines and reduce the overall quality of search results. If you decide to use subdomains, it is critical to ensure that each subdomain offers unique, valuable content that does not overlap significantly with other parts of your site.

5. Analytics and tracking challenges

From an SEO management perspective, tracking performance across subdomains can be more complicated than tracking subdirectories. Since subdomains are treated as separate entities, webmasters may need to set up separate Google Analytics accounts or configure advanced tracking to monitor performance across multiple subdomains accurately.

This added complexity can make it harder to get a holistic view of the website’s performance. It can also lead to fragmentation of data, which may hinder decision-making and optimization efforts. Setting up cross-domain tracking or ensuring that subdomain data is properly integrated with the main domain’s analytics is essential for maintaining clear insights.

6. Brand consistency and user experience

While subdomains offer technical benefits like improved site structure and targeting, they can also impact brand consistency and user experience. For users, a subdomain can feel like a separate website, especially if the design, navigation, and branding differ from the main domain.

If users perceive a subdomain as distinct from the main site, this could affect their trust and experience. Additionally, subdomains can complicate navigation and make it harder for users to understand the relationship between different parts of your website. Poor user experience can lead to increased bounce rates and lower dwell times, both of which can negatively impact SEO.

From a branding perspective, maintaining a cohesive design and user experience across subdomains is critical to ensure that visitors recognize the relationship between the main site and its subdomains. This consistency can also help build brand recognition, which may indirectly contribute to SEO success through better engagement metrics.

When to use subdomains

Despite the challenges associated with subdomains and SEO, there are certain scenarios where subdomains are the best solution:

• Internationalization: Companies with global reach may benefit from creating country-specific subdomains (fr.mypage.com, de.mypage.com). These subdomains allow for targeting location-specific content, language, and keywords.
• Distinct Products or Services: Businesses that offer multiple services or products that are distinct from each other can benefit from using subdomains to separate those offerings. For example, an e-commerce brand that sells tech products and also runs a tech blog could use a subdomain to keep the content-focused blog separate from the store.
• Content Segmentation: For large websites with substantial amounts of content, a subdomain can help organize sections like a blog, knowledge base, or customer support portal. This can make it easier for users and search engines to navigate the site.
• Different Target Audiences: Subdomains can be useful when a business has diverse target audiences, each requiring a unique marketing approach. For instance, a university might use different subdomains to cater to prospective students, current students, and alumni.

Subdomains vs. subdirectories: Which is better for SEO?

The answer to whether subdomains or subdirectories are better for SEO depends on the specific goals and needs of a website. Subdomains can offer better organization and targeting, but they come with the challenges of treating each subdomain as a separate entity for SEO purposes. Subdirectories, on the other hand, allow websites to share domain authority across sections, making it easier to rank new content.

In general, subdirectories are often the preferred choice for smaller websites that don’t need to separate their content into entirely different sections. Subdomains, however, are better suited for large websites, international businesses, or companies with diverse product or service offerings.

In a nutshell

Subdomains can have a significant impact on SEO, both positively and negatively. They allow for better organization, targeting, and content segmentation but come with the challenge of needing to build SEO authority independently from the main domain. For businesses, the choice between subdomains and subdirectories depends on factors like content strategy, audience targeting, and site structure.

When implemented properly, subdomains can coexist with a strong SEO strategy, but webmasters must ensure that each subdomain is well-optimized, unique, and part of a cohesive user experience. By understanding how subdomains affect SEO, businesses can make informed decisions about structuring their websites to meet their SEO goals.