Search Engine Optimization (SEO) may never become absolutely clear, simply because no search engine will likely ever fully divulge its algorithms. Doing so would most likely divert focus away from their “user-first” philosophy and back onto best appeasing the algorithm itself. While understandable, this often leaves the SEO community to its own devices, operating based on anecdotal evidence and accumulated experience. Never fully knowing what skyrocketed digital marketing in this or that case, or why what we observed occurred, is inevitable. The same applies to the ever-present debate of subdomain vs. subdirectory; which performs better for SEO? While Google reassures us that the two are equal, the argument persists – and for a good reason, as we’ll cover below.
Subdomain vs. Subdirectory
First and foremost, what’s a subdomain, and what’s a subdirectory? To very briefly define both, let us use a blog section example.
- A subdomain looks like this: blog.example.com.
- Instead, a subdirectory (or “subfolder”) looks like this: example.com/blog.
There are, of course, multiple technical differences between the two – and technical limitations may inform your final decision as well. But in the context of the subdomain vs. subdirectory debate, SEO-wise and technicalities aside, the functional difference is simple enough. Subdomains, as the name implies, are separate sites within the same root domain. Subdirectories, on the other hand, are essentially subfolders of the same site. In brief, that substantive difference has many marketers believe that each affects WordPress SEO differently.
What Does Google Say?
So, where does Google stand on this debate? The most thorough answer came from John Mueller, in response to a direct question – “subdomain or subfolder, which is better for SEO?”
Here, John Mueller begins with a simple, reassuring assertion; “Google Web Search is fine with using either subdomains or subdirectories”. He then proceeds to recommend “picking a setup that you can keep for longer”, on account of “changes to a site’s URL structure tend[ing] to take a bit of time to settle down in Search”. He does, however, note some key practical differences worth keeping in mind:
- “Subdirectories [are] fine for [Google]”. He explains that this helps crawlers understand that “everything’s on the same server and […] crawl it in a similar way”. He then concludes that subdomains may also help users recognize a site’s structure more easily.
- On different sections, like blogs and shops, he notes that “it’s [sometimes] easier to put them on separate subdomains”. He does reassure us that “that also works for [Google]”, only noting that subdomains need separate Search Console verification, separate settings, and separate performance tracking.
Finally, he concludes by suggesting that webmasters “use what works best for [their] setup”, and “think about [their] longer-term plans”.
Now, while it sounds reassuring as regards potential penalties, this explanation has not fully settled the subdomain vs. subdirectory debate. Why? Simply because, either being “fine” does not mean there are no benefits to one over the other. Indeed, marketers have found notable differences, often settling somewhere close to an “equal but different” perspective. That’s, of course, a crucial distinction to make, as it will affect WordPress SEO tools, final performance, and other factors.
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The Case for Subdomains
So, what’s the case to be made for either? Starting with subdomains, we have all likely seen subdomains in action for such sections as:
- Google itself uses a subdomain for its support portal (support.google.com) instead of a subdirectory.
- While many businesses do use subdirectories for blog sections, many prominent businesses use subdomains instead. A notable, oft-cited example is HubSpot, opting for blog.hubspot.com over the alternative.
- Finally, many businesses also opt for a shop.example.com structure, with HubSpot’s own shop also serving as an example here.
But why is that? If we’re to distill the main reasons down to two, those would be the following.
For shops, targeting specific locations is important in many cases. The same may apply to businesses with international audiences or aspirations. In this case, subdomains are excellent for geotargeting; do your keywords not fare well in a given country? You may simply build new keywords for that country’s version of your website. John Mueller’s comment on separate performance tracking ties into this perfectly; subdomains are different sites, albeit in the same root domain, so they will rank for different keywords.
Site Structure and Niche Authority
Similarly, the perspective of subdomains being different entities lends them to different treatment. This treatment is often twofold:
- Site structure. It’s often practically beneficial to structure sites around subdomains. Consider the aforementioned example of Google; its support page has a different purpose from its search page. By splitting the two, it establishes a clearer structure that separates the two both SEO-wise and user-wise.
- Niche authority. Building on this concept, subdomains may also establish much-needed niche authority. Consider large businesses that may need to separate their products and services, among other strategies. For them, it makes sense, SEO-wise, to have each domain build its own authority, as they target different keywords.
Of course, not all businesses will need such benefits, to begin with. That’s why subdomains offer a viable but circumstantially useful option.
The Case for Subdirectories
There is, however, another side to the subdomain vs. subdirectory debate – it wouldn’t be a debate otherwise.
The case for subdirectories, then, may begin with subdomains’ shortcomings. The most notable one, in this context, is backlink dilution. That is, subdomains will indeed build niche authority, but this autonomy means they won’t contribute to each other’s authority either. In turn, this manifests in a few different forms, the two most notable being domain authority itself and on-page SEO.
Domain Authority and Backlinks
A typical characteristic of blog sections is that they’re SEO-rich. Pages may acquire backlinks, spearhead keyword strategies, and so forth. Therefore, having them as separate domains when they don’t need to denies your website the most typical SEO benefits:
- Increased traffic – although a solid link structure and hierarchies may mitigate this somewhat.
- Domain authority
- SEO-relevant signals such as engagement
If you’re active on Twitter, you may have seen concrete proof of this benefit. If you’re not, consider this example from Andy Chadwick and this example from Stephen Kenwright. In both oft-cited cases, moving a blog section to a subdirectory over a subdomain yielded massive traffic gains. Since no other SEO changes were reportedly made, such observations make many marketers certain of the aforementioned backlink connection.
In turn, this “equal but different” perspective finds more ground on on-page SEO. Among many on page-WordPress SEO factors and techniques you can use on your website, consider the following:
- Clean, readable URLs; example.com/blog is arguably easier to read and contextualize content than blog.example.com.
- Media alt. tags and metadata; should an image find its way to image search results through its keywords, it being in a subdirectory boosts the entire site’s SEO for those keywords.
- Internal links and structure; internal links to different pages on your site also enhance WordPress SEO and consolidate hierarchies. This doesn’t just enhance crawlability, but also user navigation, producing better SEO signals through metrics like pages per session.
These and other practices and factors should further cement subdirectories as a viable option. However, as we noted above, subdomains still have their own merits.
Subdomain vs. Subdirectory: The Technical Limitations
Finally, as John Mueller also mentioned, there is one additional factor to consider in the subdomain vs. subdirectory debate. That is, the technical limitations you may encounter on the way to optimal WordPress SEO.
Indeed, sometimes we don’t have much of a choice, for reasons that don’t relate to SEO itself. For some examples, consider the following:
- Coding language discrepancies; differently-coded features such as forms may not be compatible with a main site, requiring subdomains.
- International sites; in many cases, international sites may not offer the option of subdirectories. Shopify offers an example of this, where they specifically require subdomains.
- Developer limitations and wishes; finally, developers may choose one or the other for convenience or out of necessity. Examples may include hosting support portals, blogs, and eCommerce stores on the same server, or hosting cross-CMS sections.
Thus, regardless of which option may hold the most promise, technical limitations may ultimately decide for us. That’s not to say one shouldn’t strive for the best option, but only that compromises sometimes become inevitable.
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In conclusion, then, we may best answer the question in more careful terms than one outmatching the other. For one, Google reassures us that neither carries penalties. In turn, marketers identify different benefits to each, relocating the debate to a case-by-case basis. Do you need the autonomy of subdomains, or do you prefer SEO-rich subdirectories? Will your different subdomains compete with each other for keywords? Will your subdirectories conflate products and services you’d rather keep separate or hinder user navigation? How vital is WordPress SEO to your business in relation to the user experience? There are no universal answers to such questions, only what your specific needs necessitate and what technical limitations permit.