Subdomain SEO

1. Subdomains vs. subdirectories: Which is better for SEO?
2. The importance of subdomains for your SEO
3. How subdirectories affect your SEO
4. What does Google say about Subdomain vs. Directory?
5. SEO Debate about Subdomain vs. Directory
6. Challenges with Subfolders
7. Conclusion: What is better?

When planning a new website, a migration or a redesign, there is much to consider. A key point is how you will structure the website in the future. Because the website structure has a significant effect on SEO ranking. The question arises quickly: Which is better for SEO, subdomains or directories? This very question has been concerning SEOs for many years.

In this article, we'll look at the difference between directories and subdomains in terms of SEO, the challenges both options entail, and which option is right for you.

Subdomains vs. subdirectories: Which is better for SEO?

A subdomain is a sub-area of the main domain. Your blog, webshop or support area could be a subdomain, for example, to separate the content from the rest of your website. It could look like this: https://support.omr.com/.

A subdirectory is located under the main domain and contains thematically related content, e.g. like here: https://omr.com/de/reviews. Subdirectories, also called subfolders, therefore do not have an independent web address. Access is via a folder on your main website.

You can structure the URL hierarchy of your website using both subdomains and subdirectories.

You can also combine subdomains and subdirectories. To illustrate this, let's look at an example URL:

The clearer your content structure and the relationships between the individual pages are, the easier it is for search engines to index your website. This has a direct impact on the ranking of your website in a search query. A good website structure also offers more opportunities for internal linking, which also positively influences your rankings.

The importance of subdomains for your SEO

Subdomains are considered separate websites by search engines. This means that you can appear in the search results individually with each subdomain. You must register them in the Google Search Console.

Subdomains can be helpful to avoid Keyword Cannibalism between your main domain and your blog or another content-heavy page on your website. If you have multiple subdomains, Google considers these as a whole, although they are still treated as separate websites - with their own content, design and branding. Google recognizes similarities between the subdomains, such as the same domain name.

How subdirectories affect your SEO

Subdirectories clearly show search engines that they are part of a larger website. This simplifies crawling. By using subdirectories, you bundle your keywords and link equity on a single domain. This in turn benefits your domain authority.

Breaking up your content into subdirectories can boost your overall ranking and thus drive traffic to your website, instead of spreading it across your subdomains. This is especially true for blogs.

If you use subdomains, you distribute keywords and link equity, which can weaken your domain authority. Then you have to put more work into each subdomain to achieve a good ranking.

What does Google say about Subdomain vs. Directory?

A question that all SEOs are concerned with is: Which is better for SEO, subdomain or subdirectory? John Müller, Webmaster Trends Analyst at Google, says in this YouTube video:

"Google Web Search is fine with using either subdomains or subdirectories (…) So in short, use what works best for your setup and think about your longer-term plans when picking one or the other."

So the answer to the question of whether subdomains or subdirectories are better for SEO is a clear "it doesn't really matter". But it also depends on what's easier for you to set up and what your plans are.

But John Müller also says about subdomains: "We do have to learn to crawl them separately, but for the most part, that’s just a formality for the first few days."

This statement in combination with case studies about subdomain vs. subdirectory fuels the debate that has been going on for years again and again.

SEO Debate about Subdomain vs. Directory

Which website structure is better for SEO? In this debate, there are two camps: Some believe that Google treats subdomains as separate units. This means that a subdomain has its own ranking, independent of the main domain. Others interpret John Müller's statement to mean that subdomains and subfolders are essentially identical for Google. For Google, it is almost irrelevant whether you choose subdomains or subdirectories.

Florian Elbers via Twitter

And what is really the case? The Twitter community seems particularly hot to discuss the topic.

Term frequency via Twitter

Aleyda via Twitter

FayeWatt via Twitter

Although many experiences suggest that subdirectories instead of subdomains are the better choice for SEO, there are some challenges in implementation. You should also keep in mind that switch from subdomain to directory often refers to blogs. High-quality and thematically appropriate content with good links leads to a drastic increase in traffic in these cases.

Challenges with Subfolders

Keyword Cannibalism

Keyword Cannibalism can occur if you rank with several subpages of your domain for the same keyword. Each URL should rank exclusively for a specific focus keyword. Make sure you have a good overview of your subfolders and their keywords.

Separate multiple brands under a parent brand

If you have various offers with multiple brands and different content, subdirectories as the only separation can be confusing. Very precise planning of the website architecture with a focus on user-friendliness is absolutely necessary here.

Different Requirements

An online shop requires a different SEO strategy than a blog. If everything runs on one main domain, separated only by subfolders, this can cause difficulties. Technically, an online shop also has characteristics that may not integrate into your website depending on the content management system (CMS).

Duplicate Content

You need to ensure that the content in every subfolder on your website is unique. Otherwise, you may lose rankings due to Duplicate Content. For multiple language and country versions, it is advisable for SEO purposes to use subdomains or multiple top-level domains.

Conclusion: What is better?

Which URL structure is better for you depends on what content or services you want to offer on your website and how extensive the website is. Companies expanding into foreign markets should choose subdomains. This allows keywords to be chosen separately in the local language for each market and a better placement in search results can be more easily achieved.

If you have different target audiences and different products for them, it may also be a good idea to create subdomains. However, for small companies, this is usually not necessary.

Here is a brief summary of the pros and cons of subdomains and subdirectories:

Advantages of Subdomains:

• useful for structuring very large websites
• beneficial for branding with multiple brands
• can be used for a test website
• Separation of different content

Disadvantages of Subdomains:

• may be difficult to rank high with them
• higher administrative effort
• are considered as a separate website, don't support any link equity

Advantages of Subdirectories:

• connect all content on one common website
• Link equity is passed on to the main domain
• can improve website traffic and keyword rankings

Disadvantages of Subdirectories:

• require a high degree of strategic and content planning for large websites
• clear separation of brands and target groups is difficult

There is no blanket answer to the question of whether subdomains or subdirectories are better for SEO. It depends entirely on your strategy and your goals. In most cases, however, subdirectories are the better choice to grow organically, improve ranking and visibility.

A main domain strengthens the bundling of your link authority and seems easier for Google to index. The administrative effort for you is also lower with just one domain. Besides the question of what is better for SEO, you should mainly ask what is better for the users of your website. This is also what Danny Sullivan, Google's contact for Google search, finds.

Dannysullivan via Twitter