Subdomains, subfolders and separate domains: how to organise a growing site
When a section belongs in a folder, when it belongs on a subdomain, and when it deserves its own domain, with the SEO and maintenance consequences of each.
The short answer
A growing website accumulates sections: a blog, a knowledge base, a portal, a store, a careers page, a second language, a second brand. Each can live in a subfolder of the main site, on a subdomain, or on a separate domain, and the choice has consequences for search ranking, maintenance and identity. A subfolder keeps the content inside one site: it shares the domain’s ranking strength, is built and maintained with everything else, and is the right default for anything that is content. A subdomain is technically a separate site under your name: right for a separate application with its own hosting and code, such as a portal, a booking tool or a store on another platform, and wrong for content that should help the main site rank. A separate domain is a separate brand, justified only when the audience or identity is genuinely different. Default to folders for content, subdomains for applications, and separate domains only for separate brands.
Comparing the three
| Option | Example | Search engines treat it as | Maintenance | Right for |
|---|---|---|---|---|
| Subfolder | ourdomain/knowledge | Part of the main site; strength shared | One build, one deploy, one design | Content: blog, knowledge, cases, languages, locations |
| Subdomain | portal.ourdomain | Largely a separate site under the same organisation | Separate hosting and code; shared DNS and certificates | Applications: portals, booking, stores on other platforms, status, docs |
| Separate domain | otherbrand.example | An unrelated site | Entirely separate; second domain to protect | A distinct brand with its own audience |
Deciding for a new section
- Is it content or an application? Content goes in a folder. Applications go on a subdomain.
- Does it share the main site’s design and build? If yes, folder. If it runs on a different platform, subdomain.
- Does it serve the same audience under the same brand? If yes, folder or subdomain. If a genuinely different brand, separate domain.
- Will it help the main site be found? If yes, folder, always.
- Is there a technical constraint, such as a provider that only supports its own domain or a subdomain? Then subdomain, with the main site linking to it clearly.
Languages and markets
Languages usually belong in folders on one domain, with each language declared so search engines serve the right one. Separate country domains make sense for large operations with distinct market presence and the budget to build each domain’s strength separately, and are overkill for a small business. Locations follow the same logic: pages within the site rather than a domain per city.
What this means for you
Put content in subfolders of your main site, put applications on subdomains, and buy a separate domain only for a separate brand. That structure concentrates ranking strength, keeps maintenance in one place and gives visitors one coherent site. When you inherit a scattered setup, consolidate content into folders with redirects, and keep the subdomains for the things that are genuinely separate systems.
Frequently asked questions
Should our blog be on blog.ourdomain or ourdomain/blog?
In the folder. Content that exists to help the business be found should live inside the main site so the domain's strength and the content's strength reinforce each other, and so it is designed, built and maintained as part of the same site. Subdomains are treated as more separate by search engines and split your effort.
When is a subdomain the right choice?
When the thing is a separate application rather than content: a customer portal, a booking system, a store on a different platform, a status page, a documentation tool. These have their own hosting, their own code and often their own provider, and a subdomain keeps them under your name without forcing them into the main site's build.
Our company runs two brands. One domain or two?
Two, if the brands have different audiences and would confuse each other's visitors on one site. One, with sections, if they are lines of the same business and share customers. The test is whether a visitor arriving for one brand would be surprised or put off by the other. Domain count should follow brand strategy, not the other way round.