Web & SEO
What is a subdomain?
A subdomain is a distinct section of a website that lives at its own address in front of the main domain, such as shop.example.com.
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Technical definition
A subdomain is a prefix added to a registered domain that resolves to its own destination. In shop.example.com, shop is the subdomain, example is the domain, and com is the top-level domain. Each subdomain is configured through a DNS record and can point to a different server, platform, or application than the root domain.
Search engines treat a subdomain as a related but separate property. Authority earned on the root domain does not transfer to a subdomain in full, which is the practical difference between putting content at blog.example.com and example.com/blog.
In plain terms
Think of your domain as a building and subdomains as separate entrances. Same address, different door, and what is behind each door can be run by a different system.
A store on Shopify, a help center on a support platform, and a marketing site on your own builder can all sit under one brand this way, each at its own subdomain.
Why it matters
The decision most small businesses face is subdomain or folder. A folder, such as example.com/blog, keeps everything under one roof and lets every page you publish strengthen the same domain. A subdomain splits that effort in two.
Use a subdomain when the content genuinely needs to run somewhere else, such as a store on a hosted ecommerce platform or a help center on a support tool. Use a folder when you have the choice, because concentrated authority is worth more than tidy separation. Agencies get asked to undo subdomain decisions more often than any other structural choice, and undoing one means a full migration with redirects.
