When to use subdomains versus subfolders in SEO

The choice between subdomains and subfolders seems technical at first glance. Yet this decision has direct implications for your organic findability. From an SEO point of view, it is not only an architectural issue, but also a strategic choice.

What is the difference between a subdomain and a subfolder?

A subdomain is technically a separate domain within your main site. Think blog.yourdomain.com. Google treats this as a separate entity in many cases.

A subfolder sits within the same domain path, such as yourdomain.com/blog. Search engines see this structure as part of the main domain, and therefore part of the accumulated domain authority. (1)

While both variations work well, there is such a thing as the best choice. Among other things, your decision determines how your authority is built, how link equity is distributed and how easily search engines make connections between the main site and the content.

Why subfolders are usually preferred

In most SEO scenarios, subfolders are the safest and most effective choice. They benefit directly from the authority and thematic context of the main section of your site. New content is indexed and ranked faster, and backlinks to subpages contribute to the main domain. The thematic focus remains clear and consolidated.

Especially when I’m working on a strong, central domain position within a particular topic, I opt for a subfolder structure. You strengthen your topical authority and avoid fragmentation.

When a subdomain does make sense

There are situations in which a subdomain is indeed the better choice. Think of scenarios in which your content is clearly different from the rest of the site (such as a community, web shop or support environment). Also consider scenarios in which your technical systems or CMSs need to remain separate. You may also need international targeting, where separate content structures for each country are more manageable.

In those cases, a subdomain offers organizational and technical freedom, even though it requires more effort SEO-wise to build authority. (2)

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Google’s position on subdomains

Google states that it can index and understand both subdomains and subfolders just fine. However, I often see subdomains often build authority more slowly. This makes it harder for your content to become contextually connected to the main site. So basically, work from scratch to build the same trust that you automatically bring with a subfolder.

That doesn’t mean that subdomains are necessarily a disadvantage, but it does mean that you should make a conscious decision to use them. There should be a clear purpose, preferably with support from a separate content and linking strategy.

Technical considerations

Besides SEO, there are also technical considerations that can influence your choice. Important points are hosting and manageability (in fact, subdomains can be hosted separately). Access management, caching and performance tweaks are also important for each component. Subfolders share data in analytics by default. Subdomains require additional configuration

In such cases for SEO, I make sure that crawlability is guaranteed through clear internal links and structure. Consistency in technical settings and clear internal link structure are essential for this.

Avoid hybrid structures

I often see people combining the two structures without a clear plan. A blog on a subdomain, a knowledge base in a subfolder, a landing page on yet another subdomain: this leads to confusion in thematic focus, disrupted internal linking and scattered authority.

I recommend choosing one clear structure, based on your long-term goals. Stick to it consistently.

Considerations for hybrid strategies

In some cases, though, a hybrid approach, where you deploy both subdomains and subfolders, is an appropriate solution. Consider situations where certain components need to remain technically highly separated (such as a support portal or shop), but where you want to keep the main structure under one domain.

Be aware that this places higher demands on your internal link structure and crawl budget. Hybrid setups require clear prioritization of SEO signals to avoid fragmentation.

Summary

The choice between subdomains and subfolders is strategic. Do you want to maximize SEO results within a central theme? Then a subfolder is the right choice in most cases.

Only when there are substantive or technical reasons to separate content from the main site is a subdomain justified. Weigh the benefits, consider the impact on your architecture and make a choice that fits your scalability as well as your findability strategy.