Ever wondered what the heck is the difference between a domain and a subdomain?

If you’ve spent even a little time building websites or trying to understand how the internet works, you’ve probably seen both of these terms.

And if you’re like most people, you might be thinking, “Aren’t they basically the same thing?”

Nope! They’re actually quite different, and understanding the difference is super important if you want to set up your website correctly, especially when it comes to SEO.

So let’s break down what domains and subdomains actually are, why they matter, and when you should use each one.

Domains vs. Subdomains: What’s the Difference?

What exactly is a domain?

A domain is your main website address – the thing people type into their browser to find you online. It’s like your digital home address.

For example, google.com is a domain. facebook.com is a domain. They’re the primary identifiers for these websites.

Domains typically have two parts:

• The unique name (like “google” or “facebook”)
• The top-level domain or TLD (.com, .org, .net, etc.)

When you “own” a domain, you’ve basically rented the right to use that address from a domain registrar. This gives you the foundation for your entire web presence.

Why are domains important? Because they’re your digital identity – your brand online. They’re also what people remember and share with others.

What about subdomains?

A subdomain is like a separate room or section in your domain’s house.

It appears as a prefix before your main domain name, looking something like this: blog.example.com or shop.example.com

The key thing to understand: subdomains are still part of your main domain, but they function as distinct sections that can have their own content, design, and even technology stack.

Some common examples:

• mail.google.com (Gmail)
• docs.google.com (Google Docs)
• support.apple.com (Apple’s help center)

Each of these is a different service or section, but they’re all under the main brand’s domain umbrella.

Key differences that actually matter

Feature	Domain	Subdomain
Independence	Completely standalone	Connected to main domain
SEO impact	Builds its own authority	Treated mostly as separate site
Use case	Main brand presence	Specialized content sections
Cost	Annual registration fee	Usually free (included with domain)
Setup	Requires domain purchase	Created through DNS settings

The most important thing to remember: search engines like Google often treat subdomains as separate websites for ranking purposes. This isn’t always a good thing!

SEO implications you should know about

This is where things get interesting (and potentially tricky).

While Google has gone back and forth on exactly how they treat subdomains, the current consensus is that subdomains don’t fully share the SEO benefits with the main domain.

What does this mean in practice?

• If your blog lives at blog.example.com rather than example.com/blog, it might not boost your main domain’s rankings as effectively
• Backlinks to a subdomain don’t necessarily pass the same authority to your main domain
• Each subdomain essentially starts with a “fresh” SEO profile

This is why many SEO experts recommend using subdirectories (like example.com/blog) instead of subdomains for key content.

Research from Moz actually shows that subdirectories tend to perform better for most sites in terms of organic search rankings.

However, there are some cases where subdomains make perfect sense despite the SEO considerations. For example, when you’re targeting completely different audiences or providing very distinct services.

When should you use a domain vs. a subdomain?

Use a domain when:

• You want a completely separate brand identity
• The content/purpose has minimal connection to your other websites
• You’re starting a new business or venture
• You need full SEO independence

Use a subdomain when:

• You want to create a distinct section that’s still connected to your main brand
• You need technical separation (different server or platform)
• You’re targeting different geographic regions or languages
• You’re providing a specialized tool or service under your main brand umbrella

For example, Shopify uses partners.shopify.com for their partner program because it’s a specialized section with different functionality but still clearly part of the Shopify ecosystem.

Technical differences worth knowing

Beyond the strategic differences, there are some technical aspects to consider:

• SSL certificates: Domains need their own SSL certificates for HTTPS, while subdomains either need separate certificates or a wildcard certificate
• DNS management: Subdomains require additional DNS records to configure
• Analytics tracking: You’ll need to set up cross-domain tracking to see the complete user journey across domains and subdomains
• Cookies: By default, cookies aren’t shared between domains or even subdomains

According to Google’s developer documentation, there are also implications for how search engines crawl and index your content depending on your structure.

Real-world examples

Let’s look at how some major companies structure their web presence:

GitHub:

• Main domain: github.com
• User pages: username.github.io (separate domain)
• Help docs: docs.github.com (subdomain)

Medium:

• Main domain: medium.com
• Publications: publication-name.medium.com (subdomains)

Amazon:

• Main store: amazon.com
• AWS cloud services: aws.amazon.com (subdomain)
• Prime Video: primevideo.com (separate domain)

Notice how companies make different choices based on how connected or separate they want services to appear to users and search engines.

Making the right choice for your website

So what’s the bottom line? Should you use a subdomain or stick with your main domain?

Ask yourself these questions:

1. Is this content core to my main brand/business? (If yes, probably use main domain)
2. Do I need completely different design or functionality? (If yes, subdomain might make sense)
3. How important is SEO for this content? (If very important, main domain usually wins)
4. Am I targeting a completely different audience? (If yes, subdomain or even new domain could work)

According to Search Engine Journal, most businesses should default to using subdirectories (folders on their main domain) unless they have specific technical reasons not to.

Remember: there’s no one-size-fits-all answer. Your specific business needs, technical requirements, and marketing goals should guide this decision.

The most important thing is to be deliberate and strategic about your choice, understanding the tradeoffs involved.

And if you’re really stuck, you can always consult with an SEO professional who can analyze your specific situation and recommend the best approach for your unique needs.

What domain structure questions do you have? Drop them in the comments below!