What is a subdomain? A plain-English explanation
A subdomain is a separate section of a website that sits in front of the main domain, like blog.example.com or shop.example.com, where 'blog' and 'shop' are the subdomains. It lets you organise distinct parts of a site, such as a store, blog, or support centre, under your main domain.
What a subdomain is, how it differs from a subfolder and a domain, common examples, and when to use one, explained simply for South African businesses and site owners.
TL;DR: Quick Answer
Basic South African brochure sites: R8,000-R20,000. Custom business websites with SEO and copywriting: R20,000-R50,000. E-commerce: R40,000-R150,000+. The five cost drivers that create the biggest price variation are: scope and number of pages, custom vs template design, professional copywriting, integrations (payment gateways, booking systems, CRM), and on-page SEO included at build stage. Always add 15-25% for hosting, maintenance and content updates in year one.
Key takeaways
- Very cheap quotes (under R5,000) almost always exclude copywriting, SEO, custom design and post-launch support
- Professional copywriting can represent 20-35% of a total website project cost, and is worth it for search visibility
- On-page SEO built into the website at launch costs a fraction of what it costs to retrofit after the site is live
- Hosting, SSL, domain and maintenance add R3,000-R10,000 per year on top of build cost
- E-commerce adds significant cost due to payment gateway integrations, product data, security requirements and checkout UX
- Timeline and client responsiveness directly affect cost: slow feedback rounds extend agency hours
What does a subdomain look like?
A web address has parts. In blog.example.com, 'example.com' is the main domain and 'blog' is the subdomain, the bit before the main domain name. You can create many subdomains under one domain: shop.example.com, support.example.com, app.example.com.
Each subdomain can hold a distinct section of your online presence while still belonging to your main domain. Common real-world examples include a separate store, a help centre, a blog, or a web app. The subdomain signals that this is a related but distinct part of the overall site.
How is a subdomain different from a subfolder?
This is the distinction that matters most. A subdomain comes before the domain (blog.example.com); a subfolder comes after it (example.com/blog). They look similar but search engines often treat them differently.
| Type | Example | SEO treatment |
|---|---|---|
| Subdomain | blog.example.com | Often treated as a separate site |
| Subfolder | example.com/blog | Part of the main site, shares authority |
| Domain | example.com | The main site itself |
Because a subfolder is clearly part of the main site, the SEO authority it builds usually benefits the whole domain. A subdomain may need to build some of its authority more independently.
When should you use a subdomain?
Use a subdomain when a section is genuinely separate in purpose, technology, or audience. A web application that runs on different software, a help centre on a third-party platform, or a regional site for a different country are all sensible subdomain uses.
The common mistake is putting a blog on a subdomain (blog.example.com) when it would serve SEO better as a subfolder (example.com/blog). For most content meant to strengthen your main site's rankings, a subfolder is the safer choice, because it keeps the authority consolidated under one domain.
Why does the choice affect SEO?
Search engines build a picture of a site's authority over time. When all your content sits under one domain in subfolders, that authority consolidates and every page benefits. When content is split across subdomains, the authority can fragment, with each subdomain having to earn some standing of its own.
This is why the subdomain-versus-subfolder decision is an SEO decision, not just a technical one. For content whose job is to support your main site's rankings, like a blog or resource centre, a subfolder usually wins. Reserve subdomains for sections that are genuinely distinct and do not need to share that authority.
Subdomain or subfolder: which should you choose?
For most businesses, the default should be a subfolder, because it keeps SEO authority consolidated and is simpler to manage. Put your blog, resources, and service pages under your main domain unless there is a clear reason not to.
Choose a subdomain when the section is technically or organisationally separate, a web app, a support platform, a distinct regional site, where the benefits of separation outweigh the SEO trade-off. When in doubt, a subfolder is the lower-risk choice for content that should strengthen your main site.
For how site structure affects rankings, see our guide to website development and SEO and our glossary.
Frequently asked questions
What is a subdomain?
A subdomain is a separate section of a website sitting in front of the main domain, like blog.example.com or shop.example.com, where 'blog' and 'shop' are the subdomains. It organises distinct parts of a site under your main domain.
What is the difference between a subdomain and a subfolder?
A subdomain comes before the domain (blog.example.com); a subfolder comes after it (example.com/blog). Search engines often treat a subdomain as a somewhat separate site, while a subfolder is clearly part of the main site and shares its SEO authority.
When should I use a subdomain?
Use a subdomain when a section is genuinely separate in purpose, technology, or audience, such as a web app, a help centre on another platform, or a regional site. For most content meant to strengthen your main site, a subfolder is the safer choice.
Why does subdomain versus subfolder matter for SEO?
Search engines consolidate authority under one domain. Content in subfolders benefits the whole site, while content split across subdomains can fragment authority, with each subdomain earning some standing of its own. So the choice is an SEO decision, not just technical.
Should my blog be on a subdomain or subfolder?
Usually a subfolder (example.com/blog), because it keeps SEO authority consolidated under your main domain and benefits the whole site. Reserve subdomains for genuinely separate sections like apps or support platforms that do not need to share that authority.