When adding a blog to your website it’s often much easier to integrate your content management system (CMS) on a subdomain, but often this isn’t the best-case scenario. 

Popular platforms such as WordPress and Shopify typically don’t allow you to install a brand new CMS into a subfolder but it is allowed on a subdomain.

For instance, you’ll run into problems if you have an eCommerce store running on Shopify – example.com – and you try to install a WordPress CMS on a subfolder of that domain – example.com/blog. 

It’s easy to accept the alternative and put your SEO blog on a subdomain but this will ultimately lead to technical SEO or organic traffic problems further down the line. As a growth marketing agency we’ve seen this a ton of times and this is usually the #1 reason why webmasters opt for a subdomain rather than a subdirectory; so we’re very familiar with the issues you may run into.

Before deciding whether a subdomain or subdirectory is the best option for you it’s important to understand what the purpose of the blog is for and what subdomains and subdirectories are specially used for.

Subdomain Structure

Subdomains can be beneficial for many reasons but they can also be harmful if used incorrectly. Let’s talk about how and when to use a subdomain. 

Simply put, a subdomain is an add-on to your primary domain. The main takeaway here is that a subdomain doesn’t automatically receive the same domain authority as your primary domain, the way a subdirectory does. 

It’s important to understand that in most cases, a subdomain is treated as an entirely separate domain. That may mean that you need to pay extra to incorporate tools and software from your primary domain to your subdomain. You’ll also have to verify each subdomain separately and set up tracking for each separate subdomain. 

Subdomains are great when you need to separate sections of your website that have enough content to warrant their own website and don’t need the domain authority from your primary domain. Here are a few examples:

Good subdomain uses:

• An application behind a login that isn’t being indexed in search engines.
• Support website with troubleshooting and knowledgebase articles or forums.
• A merch store on a non-eCommerce website. 
• Any content that is completely different and/or secondary to your primary website.

This is not an exhaustive list and there are always exceptions, for instance, if your website is a single-page web application then it makes sense to have your blog on a subdomain so as not to interfere with the functionality of the application. 

Bad subdomain uses:

• Translated language versions of your primary website. 
• Your primary blog that is driving organic traffic. 
• Core products or features of your primary website.

Subdirectory Structure

A subdirectory is a sub-section of your primary website and is recognized by crawlers as such. This means that you retain all the domain authority that your primary domain has and continue to build on your website’s comprehensive coverage.

Subdirectories are the preferred option if your content strategy revolves around the same topic as your primary domain and is being used to drive high-quality organic traffic. 

How do subdirectories and subdomains affect SEO?

Google is able to crawl both subdomains and subdirectories so you won’t be penalized for either approach as long as you’ve set each up correctly on the backend. With that being said, there is more technical SEO work needed to effectively index and rank pages on your subdomain. Also, crawlers have come a long way at recognizing subdomains and attributing that traffic and rankings to your domain, but they still have a long way to go.

Subdomains should be verified and submitted to Google Search Console with an XML sitemap. 

Using a subdirectory strategy concentrates your keywords onto a single domain while the subdomain strategy spreads your keywords across multiple distinct domains. This essentially establishes the subdomain as its own website and is treated as such by crawlers. For SEO purposes, this is putting us at a disadvantage compared to a subdirectory, which is treated as a new section added to your primary domain. 

Should you put a blog on a subdomain or subdirectory?

When talking about an SEO blog, the answer is almost always going to be a subdirectory. Building your blog on a subdirectory allows you to build on top of the existing domain authority that your root domain has built up over time. 

For example, if the domain authority (DA) of your root domain is 85 that means that your blog is also starting at a DA of 85. If you were to add a subdomain to a root domain of 85 there is no specific information from Google to figure out exactly what the DA of that subdomain is. For that reason, it’s best to start a new blog on your root domain so that you don’t have to re-build all the authority that you’ve built up over the years. 

Conclusion

If you’re just launching your blog and looking to optimize it for SEO, consider using a subdirectory over a subdomain. Driving more organic traffic to your root domain and increasing your domain authority is something that I’m sure you’re already working on and using a subdirectory strategy will help improve your effectiveness.

If your organic traffic is suffering and some of your top-performing pages are on subdomains you might want to think about migrating them to the root domain. 

Derek Coleman

Derek is a digital marketer based in Boston, Massachusetts with almost a decade of hands-on SEO experience. He finds it meaningful, challenging, and exciting to develop, test, and implement new SEO strategies. When he’s not auditing websites and optimizing content he’s usually backpacking and exploring new cultures.