Subdomains explained

What is a subdomain?

A subdomain is an extension of your domain name that sits to the left of the main domain. Your root domain is yourbusiness.com. A subdomain adds a prefix:

• www.yourbusiness.com: the most common subdomain (the www prefix)
• shop.yourbusiness.com: might host an e-commerce store
• blog.yourbusiness.com: might host a blog on a different platform
• app.yourbusiness.com: might host a software application
• mail.yourbusiness.com: often the name of a mail server that your MX records point to

You can create as many subdomains as you need. They're free: you don't pay extra to use them, and you don't need to register them separately. Each one is just a record in your DNS, so the only real ceiling is however many records your DNS provider allows.

How subdomains work

A subdomain is just a DNS record. To create one, you add an A record or CNAME record for the subdomain in your DNS settings.

For example, to create shop.yourbusiness.com, you'd add a DNS record:

Or, if the shop platform provides a URL rather than an IP address:

The subdomain can then point to a completely different server or platform than your main website.

Common uses for subdomains

Subdomains vs subdirectories

You can structure your site in two ways:

You'll read a lot of confident SEO advice on this. Google's own guidance doesn't crown a winner. It recommends "creating a simple URL structure" and organizing content "so that URLs are constructed logically and in a manner that is most intelligible to humans." Where Google does compare the two directly (for country and language versions of a site), it lists both as easy to set up, and the trade-off it names is practical rather than about ranking: a subdirectory is lower maintenance because everything is on the same host, while a subdomain makes it easier to keep the two sites separate and to run them on different servers.

For most clients the practical side decides it: a subdirectory keeps everything on one site, one certificate, and one set of tools, which is usually simpler for something like a blog. Subdomains make more sense when the content is genuinely separate: a different platform, a different product, a different team.

Common questions

Related guides

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• Domains & DNS, explained simplyWhat is DNS?A plain-English explanation of the Domain Name System: how it works, why it matters, and what it has to do with your website and email.