What Is a Subdomain? Definition, Examples, and How to Use One

A subdomain is a prefix attached to your main domain name that creates a separate section of your website with its own address. For example, in blog.yoursite.com, blog is the subdomain. Subdomains let you organize large websites into distinct areas — each with its own content, design, or even server — without needing to register a brand-new domain name.

If you're building a business website, launching an online store, or trying to make sense of how web addresses actually work, understanding subdomains is one of those foundational concepts that pays off fast. This guide covers what subdomains are, how they work, when to use them (and when not to), and how to set one up.

How a domain name is structured

Before diving into subdomains specifically, it helps to see where they sit in the anatomy of a web address.

Take this example URL: support.apple.com

• support — the subdomain

• apple — the second-level domain (the main domain name)

• .com — the top-level domain (TLD)

The domain hierarchy runs right to left. The TLD (.com, .org, .net) is at the top. Your registered domain name sits beneath it. A subdomain is a layer you add on the left side of your main domain, separated by a dot.

The most common subdomain you'll encounter is www. When you visit www.example.com, "www" is technically a subdomain — it's just so universal that most people don't think of it that way. Most modern sites strip it out or redirect automatically, so www.example.com and example.com land on the same page.

You can create as many subdomains as you need. A single domain can host dozens of subdomains, each pointing to a different section, server, or application.

What is a subdomain used for?

Subdomains solve a specific organizational problem: what do you do when part of your website is so different from the rest that it needs its own front door?

Here are the most common real-world uses:

Blogs and content hubs. Companies often host their blog at blog.company.com. This is especially common when the blog runs on a different platform than the main site.

Online stores. An e-commerce section running on a separate platform might live at shop.example.com or store.example.com, keeping transactions isolated from the main marketing site.

Customer support portals. Apple uses support.apple.com. Google uses support.google.com. A dedicated support subdomain lets you run a help center or knowledge base on specialized helpdesk software without touching the main site.

Staging and development environments. Developers frequently set up staging.yoursite.com or dev.yoursite.com to test changes before pushing them live. Anything you break on the staging subdomain stays invisible to visitors.

Regional or language variations. International companies often use country-code subdomains like fr.example.com (France), de.example.com (Germany), or en.example.com (English), each serving localized content.

Member or client portals. SaaS companies often give customers their own subdomain: yourcompany.appname.com. Each customer gets a personalized URL pointing to their own account or workspace.

APIs and developer tools. Technical endpoints often live at api.example.com or developer.example.com, separated from the consumer-facing site.

How subdomains work technically

When someone types a URL into their browser, the Domain Name System (DNS) figures out which server to send the request to. Subdomains plug into this system through DNS records.

Here's the simplified version:

1. You own example.com and control its DNS settings through your domain registrar or hosting provider.

2. You create a DNS record — typically an A record (pointing to an IP address) or a CNAME record (pointing to another domain name) — for your subdomain.

3. That record tells the DNS system: when someone requests blog.example.com, send them here.

4. Visitors who type blog.example.com get routed to whatever server or application you've pointed that record at.

Because subdomains have their own DNS records, they can point to completely different servers, IP addresses, or platforms than your main domain. Your main site might be on Wix, your support subdomain might run on Zendesk, and your staging subdomain might live on a local development server — all under the same root domain.

DNS changes take time to spread across the internet (a process called propagation), so a newly created subdomain may take anywhere from a few minutes to 48 hours to resolve consistently worldwide.

Subdomain vs subdirectory: which should you use?

This is one of the most debated questions in web development and SEO. Understanding the difference helps you make a smarter choice.

A subdirectory (also called a subfolder) is a path within your main domain: example.com/blog. A subdomain is a separate prefix: blog.example.com.

From a user perspective, both look like part of the same website. From a technical and SEO perspective, there are real differences:

• Subdomain URL structure: blog.example.com vs Subdirectory: example.com/blog

• Search engines often treat subdomains as separate sites; subdirectories are part of the main site

• Subdirectories share link equity with the root domain; subdomains don't automatically pass authority

• Subdomains can run on completely different platforms; subdirectories must share the same platform

• Subdirectory setup is simpler (create a folder); subdomains require DNS configuration

• Best for subdomains: third-party integrations, regional sites, developer environments

• Best for subdirectories: blogs and content that should strengthen the main domain

The honest answer: if you're running a blog or content section on the same platform as your main site, use a subdirectory. If you're integrating a third-party tool, spinning up a regional site, or building a developer environment that needs its own server, use a subdomain.

Subdomain vs domain: what's the difference?

A domain is the registered name you own — like yoursite.com. You pay for it, it appears in the WHOIS database, and renewing it is your responsibility.

A subdomain is a free extension of a domain you already own. You don't register subdomains separately or pay extra for them (beyond any platform-specific fees). As long as you control the DNS settings for your domain, you can create as many subdomains as you want.

However, subdomains inherit the ownership and renewal status of the root domain. If you let yoursite.com expire, every subdomain — blog.yoursite.com, shop.yoursite.com, and any others — goes down with it.

Free subdomains vs custom subdomains

There's an important distinction worth calling out here.

Free subdomains from a platform are what you get when you build a website on a platform without purchasing your own domain. You might end up with an address like yourbusiness.wixsite.com or yourbusiness.wordpress.com. These are fine for testing but look less professional than a custom domain.

Custom subdomains on your own domain are what this guide has mostly been discussing. You own the root domain (example.com), and you add prefixes to it (blog.example.com). This looks professional and keeps your brand consistent.

If you want a fully custom domain with the option to add your own subdomains later, the first step is registering a domain name. Use domain name search to check availability and buy a domain directly — Wix lets you connect, manage, and configure subdomains from your dashboard once your domain is set up.

How to set up a subdomain

The exact process depends on your hosting or website platform, but the general steps are consistent across providers.

Step 1: Access your DNS settings

Log in to your domain registrar or hosting provider and navigate to your DNS management panel. This might be labeled DNS Zone, DNS Records, or Advanced DNS.

Step 2: Create a new DNS record

Add a new record for your subdomain:

• Record type: A record (if you're pointing to an IP address) or CNAME record (if pointing to another domain name)

• Name/Host: Enter your subdomain prefix (e.g., blog for blog.yoursite.com)

• Value/Points to: The IP address or domain name of the server where your subdomain content lives

• TTL: Leave as default, or set lower (like 300 seconds) if you expect to change it soon

Step 3: Configure your server or platform

If your subdomain points to a separate application (like WordPress or a helpdesk tool), you'll need to configure that platform to recognize and serve the subdomain. Many hosted platforms have a field where you enter your custom subdomain URL.

Step 4: Wait for DNS propagation

Changes may take a few minutes to a few hours to take effect globally. Use a DNS propagation checker tool to confirm when the subdomain is resolving correctly worldwide.

Step 5: Set up SSL/HTTPS

Most hosting providers now offer free SSL certificates. Make sure your subdomain has its own SSL certificate so it loads over HTTPS rather than HTTP. Visitors and search engines both expect secure connections.

Can you have subdomains on a Wix website?

Yes. Wix supports subdomains for sites connected to a custom domain. From your Wix dashboard, you can manage subdomains under your domain settings. You can redirect a subdomain to a specific page on your Wix site, or point it externally to a third-party tool. If you don't yet have a custom domain, you can buy a domain and connect it to your Wix site, after which subdomain management becomes available.

SEO considerations for subdomains

A few things worth knowing if rankings matter to you:

• Google crawls and indexes subdomains — content on your subdomain can rank in search results, just like content on your main domain

• Subdomains may be treated as separate entities — backlinks and authority don't always pass cleanly between a subdomain and its root domain

• Each subdomain needs its own SEO work — build backlinks to it, optimize on-page SEO, and verify it separately in Google Search Console

• Subdomains don't hurt your main domain — a poorly performing subdomain won't directly drag down your root domain's rankings

• Technical SEO applies independently — SSL certificates, sitemaps, robots.txt files, and page speed all need to be configured per subdomain

  
  

Common mistakes to avoid

Creating subdomains when a subdirectory would do. If your blog runs on the same CMS as your main site, putting it at blog.example.com instead of example.com/blog splits your link authority unnecessarily.

Forgetting to secure subdomains with SSL. An HTTP subdomain triggers browser security warnings and damages your rankings.

Leaving unused subdomains live. Abandoned staging or development subdomains can expose old code, create security vulnerabilities, or confuse search engines if they accidentally get indexed.

Treating a free subdomain as a permanent home. Building your business on a free platform subdomain works for early testing, but it's not a long-term branding solution. Invest in your own domain when you're ready to look professional.

Skipping DNS propagation time. If a subdomain doesn't work immediately after you set it up, it's usually just propagation lag — not a setup error. Wait an hour or two before troubleshooting.

What is a subdomain FAQ

Is a subdomain free?

If you own a domain, creating subdomains on it costs nothing extra. You simply add DNS records. However, some website platforms charge for hosting or connecting subdomains. A free subdomain from a platform (like yourbrand.wixsite.com) is also free — but you're using their domain, not your own.

Does a subdomain count as a separate website?

Technically, it can be. A subdomain can point to a completely different server, platform, or application from the root domain. Search engines may also treat it as a distinct site. But from a user experience standpoint, a well-branded subdomain looks and feels like part of the same business.

How many subdomains can I have?

There's no strict technical limit to how many subdomains a domain can have. In practice, DNS providers may impose their own limits, but you'd have to create hundreds before hitting them. Most websites use fewer than ten.

Can a subdomain hurt my SEO?

A subdomain itself doesn't hurt SEO. The potential issue is that content on a subdomain may not strengthen your root domain's authority the way content on a subdirectory would. If that matters for your strategy, consider using a subdirectory instead.

What is the difference between a subdomain and a domain extension?

A domain extension (TLD) is the suffix at the end of a domain — .com, .org, .net, .io. A subdomain is a prefix at the beginning of an existing domain — blog.example.com. They're unrelated: you choose your TLD when registering a domain; you create subdomains after the fact through DNS settings.

Can I point a subdomain to a different hosting provider?

Yes. Because subdomains have their own DNS records, they can point to any server or hosting provider, regardless of where your root domain is hosted. This is exactly why they're useful for integrating third-party tools.

Are subdomains indexed by Google?

Yes. Google crawls and indexes subdomain content the same way it does main domain content. If you don't want a subdomain indexed (like a staging environment), use a robots.txt file or password protection to keep it out of search results.

Is www a subdomain?

Technically, yes. "www" is a subdomain of your root domain. In practice, www.example.com and example.com are usually configured to serve identical content via redirects, so the distinction rarely matters for end users.

What happens to my subdomains if my domain expires?

If your root domain expires and you don't renew it, all subdomains tied to it become inaccessible. Subdomains can't survive without the root domain they're attached to.

How do I check if a subdomain is already taken?

Subdomains aren't registered through a public registry the way domain names are — they're configured in private DNS settings. You can't search for subdomain availability the way you can for domain names. You can check whether a particular subdomain resolves by simply trying to visit it in a browser.