What Is a Subdomain?
A subdomain is a prefix attached to the left side of your main domain name, separated by a dot. The most familiar example is www, which is technically a subdomain of the root domain. Other common subdomains include blog.mybusiness.co.za, shop.mybusiness.co.za, and support.mybusiness.co.za. Each subdomain can point to a different server, run a different content management system, and operate as a functionally independent website while sharing the parent domain name.
Creating a subdomain is free and requires only a DNS record change on your domain registrar or hosting provider. Technically, you can create an unlimited number of subdomains under any domain you control. They are useful when a section of your website needs to run on a completely different platform. A company might run its main marketing website on WordPress while hosting its customer support portal on Zendesk at support.company.co.za, or its online store on Shopify at shop.company.co.za.
From an SEO perspective, the critical question with subdomains is authority. Google treats subdomains as separate entities in many contexts, meaning a subdomain does not automatically inherit the ranking authority and backlink equity that the root domain has accumulated. Content published at blog.mybusiness.co.za starts with zero authority of its own, whereas the same content at mybusiness.co.za/blog/ immediately benefits from the domain's existing strength. This is the core reason most SEO practitioners recommend subfolders over subdomains for content such as blogs, resource centres, and location pages.
Subdomain In Practice
A Johannesburg-based insurance group with multiple product lines might legitimately use subdomains to separate its car insurance, home insurance, and business insurance websites. Each product line has its own team, its own platform configuration, and very different keyword targets. In this scenario, subdomains make operational sense, and the business accepts that each subdomain must build its own SEO authority independently.
However, a small Pretoria accounting firm that wants to add a blog should use a subfolder structure, such as smithaccounting.co.za/blog/, rather than blog.smithaccounting.co.za. The subfolder approach means every blog post contributes to the authority of the main domain. New content earns links and engagement that strengthen the entire website's ability to rank, not just one isolated section. Understanding the subdomain versus subfolder debate is a foundational aspect of technical SEO that affects how quickly and how high new content can rank in South African search results.
FAQ
Is a subdomain or subfolder better for SEO?
For most content, a subfolder is better for SEO because it concentrates authority on the main domain. Content at mybusiness.co.za/blog passes link equity to the root domain, whereas blog.mybusiness.co.za is treated as a separate entity and must build its own authority. Subdomains are appropriate for technically distinct applications, such as a separate e-commerce platform or a language-specific version of your site.
Does Google treat subdomains as separate websites?
Google can treat subdomains as separate from the main domain, which means they do not automatically inherit the authority of the root domain. Google has stated that it tries to understand the relationship between a subdomain and the root, but in practice, content on a subdomain often needs to earn its own rankings independently. This is why most SEO practitioners prefer subfolders for content that should benefit from the main domain's authority.