For years, website owners, marketers, and even SEO experts have argued about which is better. One side claims it makes no difference, while the other insists that one choice is clearly superior. This isn't just an academic argument; making the wrong choice can mean leaving valuable traffic and authority on the table, essentially making your marketing efforts much harder than they need to be.
This report will cut through the noise. We’ll explore the history of this debate, look at what Google itself has said, and—most importantly—examine the real-world evidence and case studies. By the end, you’ll have a clear understanding of how subdomains and subdirectories work, how search engines see them, and which structure is almost always the right choice for maximizing your SEO success.
Key Takeaways
For those looking for a quick summary, here are the most important findings from our deep research. This is the executive summary of the subdomain versus subdirectory debate.
The Consensus is Clear: For the vast majority of businesses, a subdirectory (yourwebsite.com/blog) is significantly better for SEO than a subdomain (blog.yourwebsite.com). This is the overwhelming consensus among SEO professionals, supported by extensive case studies.
Authority Consolidation is Key: The primary reason subdirectories win is that they keep all your SEO authority—often called "link equity" or "domain authority"—on a single domain. All the valuable links you earn to your blog posts directly boost the power of your entire website, including your main commercial pages.
Google's Official Stance: Google representatives, like John Mueller, have stated that their systems have gotten much better at understanding the relationship between a main domain and its subdomains. In theory, they can pass authority between them. However, real-world results show this process is not as efficient or reliable as the direct consolidation offered by a subdirectory.
Subdomains Can Dilute Your Power: When you place your blog on a subdomain, search engines may treat it as a separate, semi-independent website. This can split your authority. The great content on your blog might build up its own reputation, but that power doesn't fully transfer back to your main domain where you sell your products or services.
Subdirectories are Simpler: From a technical and analytical standpoint, managing one site (yourwebsite.com) is far easier than managing two (yourwebsite.com and blog.yourwebsite.com). Tracking, reporting, and site maintenance are all streamlined with a subdirectory structure.
There Are Niche Cases for Subdomains: Subdomains are not useless. They are the correct choice when you need to host something that is truly a separate business, for different geographic regions with different languages, or for a web application that is functionally distinct from your main marketing site (like app.yourwebsite.com).
What Exactly Is a Subdomain?
Before we dive deeper, let's make sure we're on the same page. Think of your main website address, yourwebsite.com, as a plot of land. A subdomain is like building a separate guest house on that same plot of land. Its address is blog.yourwebsite.com.
Technically, the "blog" part is a prefix added to your main domain name (the "root domain"). It signals a distinct section of your overall web presence. Companies use subdomains for all sorts of things. For example, Google uses them to separate its various services: mail.google.com for Gmail, docs.google.com for Google Docs, and news.google.com for Google News. Each of these is a massive, distinct product that functions independently from the main search engine. In these cases, a subdomain makes perfect sense because the purpose and audience for each are different. It helps organize a vast digital empire.
And What Is a Subdirectory?
Now, let's talk about subdirectories. If your main domain is a house, a subdirectory is simply a room inside that house. Its address looks like this: yourwebsite.com/blog.
It’s also often called a subfolder. You can see this structure all over the web. When you visit a company’s website and click on their "About Us" page, you'll often land on a URL like company.com/about-us. The /about-us part is a subdirectory. It’s part of the same core website, just in a different folder. The same logic applies to a blog. It’s just another section, another room, within the same house. This structure keeps everything under one roof, which, as we'll see, is incredibly important for SEO.
The Core Technical Difference
The main difference between the two comes down to how they are set up on a server. A subdomain requires a new DNS (Domain Name System) record to be created. It can technically be hosted on a completely different server in a different part of the world. A subdirectory, on the other hand, is just a file path within the existing website's hosting environment. This might sound like technical jargon—and it is—but this fundamental difference is what leads to all the SEO implications. Because a subdomain can be a separate entity, search engines sometimes treat it that way. A subdirectory, by its very nature, can only be part of the main entity.
How Google Views Subdomains vs. Subdirectories
This is the heart of the debate. For years, the SEO community has carefully listened to every word from Google’s representatives on this topic. Historically, back in the early days of search, Google absolutely treated subdomains as separate websites. If you had blog.yourwebsite.com, it was almost like you owned two different sites. Any SEO power your blog gained stayed with the blog. It didn't help yourwebsite.com rank.
Over time, Google has become much more sophisticated. Today, Google's official stance, often repeated by their Search Advocate John Mueller, is that their algorithms are generally able to figure out that blog.yourwebsite.com and yourwebsite.com belong to the same company. They try to pass the ranking signals, like links, between them.
However, there's a big difference between "can" and "always does perfectly." The SEO industry's collective experience and countless case studies show that this "passing of power" is not 100% efficient. Think of it like a plumbing system. A subdirectory is a single, solid pipe. All the water pressure (authority) flows through it without any loss. A subdomain is like connecting two separate pipe systems with a valve. The valve might work most of the time, but it's a point of potential failure and you might lose some pressure along the way. Why add an extra point of failure when you don't have to?
The All-Important Concept of Link Equity
To truly understand why subdirectories are better for SEO, you need to understand "link equity." Imagine that every link from another website to yours is a vote of confidence. A link from a highly respected site like a major news outlet or a top university is a very powerful vote. A link from a small, unknown blog is a less powerful vote. Link equity is the total value of all these votes pointing to your site. The more link equity you have, the higher your website can rank in search results.
When your blog is in a subdirectory (yourwebsite.com/blog), every single link you earn to any of your amazing blog posts adds to the total link equity of yourwebsite.com. The power flows seamlessly. A popular article that gets linked to by dozens of other sites directly helps your product and service pages rank higher. They are all part of the same domain.
With a subdomain, the situation is messier. A link to blog.yourwebsite.com primarily boosts the authority of the subdomain itself. While Google tries to associate this with the main domain, the transfer of power is indirect and often incomplete. You are effectively diluting your own strength by splitting it across two separate (or semi-separate) entities.
A Look at Real-World Evidence
This isn't just a theory. Many companies have publicly shared what happened when they moved their blog from a subdomain to a subdirectory. The results are often dramatic. One famous case study showed a near-instantaneous and massive jump in organic traffic right after making the switch. They didn't change the content, they just changed the URL structure. All that "trapped" link equity on the subdomain was suddenly unleashed onto the main domain, boosting the rankings of all their pages.
This pattern has been repeated time and time again. SEO agencies frequently recommend this migration as one of the first and most impactful technical fixes for a new client. The data consistently shows that consolidating content into a subdirectory structure leads to better overall keyword rankings and more organic traffic. It’s one of the closest things to a "sure thing" in the ever-changing world of SEO.
Topical Authority: Keeping Your Expertise in One Place
Another important SEO concept is "topical authority." This is Google's way of understanding that a website is a true expert on a particular subject. If you run a website about gardening and you consistently publish high-quality, in-depth articles about soil types, composting, and plant care, Google starts to see your site as an authority on gardening. As a result, it will be more likely to rank your pages for gardening-related searches.
When your blog is in a subdirectory (yourwebsite.com/blog), all of your expert content lives under one roof. Your main site, yourwebsite.com, becomes the recognized authority. This helps every page on your site, from blog posts to product pages, rank better for your target topics. You are building a powerful, unified hub of expertise.
If your blog is on a subdomain, you risk splitting this topical authority. Google might see yourwebsite.com as an expert in selling gardening tools, and blog.yourwebsite.com as an expert in gardening advice. The two reputations are related, but separate. You miss out on the powerful synergy of having your commercial pages and your informational content working together to build a single, dominant topical authority for your entire domain.
The Impact on Crawling and Indexing
Search engines use automated programs called "crawlers" or "spiders" to discover and index content on the web. Every website is given a "crawl budget," which is roughly the amount of time and resources a search engine will dedicate to crawling your site. For very large websites with millions ofpages, the crawl budget can be a real concern.
While this debate is less critical for smaller sites, the structure can still have an impact. A single site under a subdirectory structure is often simpler and more efficient for Google to crawl. All the content is clearly part of one cohesive whole, linked together internally.
A subdomain, being technically separate, may require the crawler to treat it as a new site to be discovered and assessed. Again, it adds a layer of complexity. While Google can certainly handle it, the simpler, more direct path of a subdirectory is more efficient. Efficiency in crawling can lead to faster indexing of your new content, which means it can start ranking and bringing in traffic sooner.
The Practical Side: Analytics and Maintenance
Beyond the direct SEO benefits, there are practical reasons to prefer a subdirectory. Managing your website is simply easier when everything is in one place.
Let's start with website analytics. If you use a tool like Google Analytics, tracking user behavior on a single domain (yourwebsite.com) is straightforward. You can easily see how users move from a blog post to a product page and, eventually, to making a purchase. This is called "cross-directory tracking," and it works out of the a box.
When your blog is on a subdomain, tracking that same user journey becomes more complicated. You now have to set up "cross-domain tracking." This is because, from the perspective of analytics software, yourwebsite.com and blog.yourwebsite.com are two different properties. It’s absolutely doable, but it requires extra configuration and introduces more room for error. A simple, unified setup is always better for getting clean, reliable data about how your customers are interacting with your site.
Website Maintenance and Cost
The same logic applies to the technical maintenance of your website. With a subdirectory, you have one website to update, one security certificate (SSL) to manage, and one content management system (CMS) to maintain. This simplifies things for your development team and can reduce costs.
A subdomain can sometimes require its own separate hosting plan, its own CMS installation, and its own security protocols. This might not be a big deal for a large corporation with a huge IT department, but for a small or medium-sized business, it adds unnecessary complexity and expense. Keeping your blog in a subdirectory is often the more streamlined and cost-effective option from a pure operational standpoint. It's one less thing to worry about.
When Should You Actually Use a Subdomain?
After everything we've discussed, you might think subdomains are always the wrong choice. But that's not quite true. While a subdirectory is the best option for the SEO of an integrated blog, there are specific, valid reasons why a business might choose to use a subdomain. Understanding these exceptions helps clarify why the general rule exists.
The key question to ask is: "Is this content or service fundamentally different from our core business?" If the answer is yes, a subdomain might be the right tool for the job.
Here are the most common and legitimate use cases for a subdomain:
Truly Separate Business Divisions: A large corporation like Amazon uses subdomains to separate its major, distinct business units. aws.amazon.com (Amazon Web Services) is a completely different business targeting a different audience (developers, IT professionals) than the main amazon.com retail site. In this case, trying to merge them would be confusing for users and wouldn't make sense from a branding perspective.
International Websites (Internationalization): If you have versions of your website for different countries and languages, using a subdomain is a common and effective strategy. For example, you might have fr.yourwebsite.com for France and de.yourwebsite.com for Germany. This clearly signals to both users and search engines that this version of the site is specifically for that region. While you can also use subdirectories for this (e.g., yourwebsite.com/fr), subdomains are a perfectly valid and widely used method for international SEO.
Hosting a Web Application: Often, the web application or software a company sells is functionally separate from its main marketing website. For example, a project management tool might have its marketing pages at projecttool.com, but when users log in to use the tool, they are sent to app.projecttool.com. This makes sense because the application itself requires different technology, security, and servers than the simple marketing site.
Support Portals or Knowledge Bases: Many companies host their customer support content on a subdomain like support.company.com. This content is for existing customers and serves a different purpose than the main site, which is focused on attracting new customers. Separating it can streamline operations, especially if the support portal is run using a third-party platform like Zendesk, which often defaults to a subdomain structure.
In all these cases, the content on the subdomain is not primarily intended to directly boost the SEO of the main marketing site. It serves a different purpose, and therefore, separating it makes organizational and technical sense.
Making the Switch: Migrating from Subdomain to Subdirectory
What if you're reading this and realizing your blog is currently on a subdomain? The good news is that you can fix it. Migrating your blog from a subdomain to a subdirectory is a common technical SEO project. However, it must be done very carefully to avoid losing traffic and rankings.
The most critical step is to implement proper 301 redirects. A 301 redirect is a permanent redirect that tells search engines and user browsers that a page has moved to a new address forever. You must create a redirect for every single post on your old subdomain, pointing it to its new location in the subdirectory.
For example, blog.yourwebsite.com/my-awesome-post must be 301 redirected to yourwebsite.com/blog/my-awesome-post.
If you fail to do this correctly, search engines will see all your old URLs as broken links, and you will lose all the valuable link equity those pages have accumulated over the years. Your traffic could plummet overnight. This is not a task for a novice. It's highly recommended to work with an experienced web developer or SEO professional to plan and execute the migration. They will ensure every URL is mapped correctly, test the redirects, and submit the changes to Google to ensure a smooth transition.
What to Expect After the Migration
When done correctly, the results of a subdomain-to-subdirectory migration are almost universally positive. SEOs who have managed these projects report a few common phases. First, there might be a brief period of fluctuation in traffic and rankings for a few weeks as Google processes all the changes. This is normal.
Then, as Google starts to fully credit the main domain with all the authority that was previously "stuck" on the subdomain, you should begin to see a significant and sustained increase in organic traffic. This lift doesn't just apply to your blog posts; it often boosts the rankings of your most important commercial pages as well, because the entire domain is now stronger. It’s a powerful demonstration of the principle of authority consolidation in action.
The Final Verdict: Subdirectory for the Win
The debate between subdomains and subdirectories has persisted for a long time, but the evidence from the real world is clear and compelling. For any business whose blog is an integral part of its marketing strategy—designed to attract customers, build authority, and drive traffic to its products or services—a subdirectory is the superior choice.
By placing your blog at yourwebsite.com/blog, you ensure that all the hard work you put into creating great content directly contributes to the SEO strength of your entire website. You consolidate your link equity, build unified topical authority, and simplify your analytics and maintenance. It is the most direct and efficient way to leverage content to achieve your business goals.
Subdomains have their place. They are the right tool for cordoning off distinct parts of a business, for international sites, or for hosting separate applications. But for your main company blog, choosing a subdomain is often an unnecessary and self-inflicted wound to your SEO potential. It's like deciding to build two decent houses instead of one great mansion. Why split your resources when you can combine them to build something much more powerful? Choose the subdirectory.
Frequently Asked Questions (FAQs)
1. Will I get penalized by Google for using a subdomain for my blog?
No, you will not be "penalized" for using a subdomain. Google is perfectly capable of crawling and indexing subdomains. The issue is not one of penalty, but of opportunity cost. By using a subdomain, you are likely not maximizing your SEO potential because you are splitting your site's authority, whereas a subdirectory consolidates it. It's less about punishment and more about not getting the full reward for your efforts.
2. Is it ever too late to move my blog from a subdomain to a subdirectory?
It's almost never too late. In fact, the more authority your blog on a subdomain has built up, the more you stand to gain from migrating it correctly. An older blog with many backlinks has a lot of "trapped" authority. Moving it to a subdirectory can unlock that power for your main domain. The key is to execute the migration with flawless 301 redirects to preserve your existing rankings and link equity.
3. What if my blogging platform, like HubSpot or Medium, forces me to use a subdomain?
This is a common challenge. Some platforms are designed to run on subdomains by default. In this situation, you have to weigh the benefits of the platform (ease of use, built-in features) against the SEO cost. Some modern platforms offer ways to configure them within a subdirectory using a setup called a "reverse proxy," but this is a complex technical task. If that's not possible, you must decide if the platform is valuable enough to justify the split in domain authority. For many serious businesses, the long-term SEO benefits of a subdirectory outweigh the convenience of such platforms.
4. Does this debate also apply to e-commerce stores? Should my shop be on shop.website.com or website.com/shop?
Yes, the exact same logic applies. If your store is an integral part of your business, it should almost always be in a subdirectory (website.com/shop). This allows your product pages and category pages to benefit from the authority of your main domain and any content you produce. You would only use a subdomain like shop.website.com if the shop was a completely separate business venture, like an employee-only merchandise store that isn't meant for the public.
5. How can I tell how Google sees my subdomain?
One way to get a rough idea is to use Google Search Console. If you have verified both your main domain and your subdomain as separate properties, you can look at the performance reports for each. If your subdomain has a lot of backlinks and rankings but your main domain is struggling, it's a sign that authority may not be passing between them effectively. A more definitive test is the migration itself; a significant traffic lift after moving to a subdirectory is the clearest proof that your authority was previously split.
References & Further Reading
Ahrefs. (2021). Subdomain vs. Subdirectory: Which Is Better for SEO?
Google. (2017). Google Search Central: Subdomain or subfolder, which is better for SEO? [Video]. YouTube.
Moz. (2021). Subdomains vs. Subfolders: Which is Better for SEO?
Search Engine Journal. (2023). Subdomain vs. Subdirectory: Which Is Better for SEO & Why?
Semrush. (2023). Subdomain vs. Subdirectory: Which One Is the SEO-Friendlier Option?
Fishkin, R. (2018). Should We Host Our New Product on a Subdomain or Subfolder? SparkToro.
Path Interactive. (2021). Subdomain vs. Subdirectory SEO: A Technical Guide.
Hall, A. (2020). I analysed the SEO impact of Subdomains vs Subfolders. Here's what I found.
Cyrus, S. (2022). Subdomain vs Subfolder for SEO. Zyppy.
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