Subdomain
DomainsSubdomain is a DNS-based subdivision of a domain name that creates a separate hostname under the same registered domain, such as blog.example.com. It can point to different servers, IP addresses, or directories, allowing distinct sites, apps, or environments to run independently while sharing the parent domain. Subdomains are commonly used to organize content, isolate services, and manage deployments without buying new domains.
How It Works
A subdomain is created by adding a label to the left of a domain (for example, "shop" in shop.example.com). Technically, it is defined through DNS records in the domain zone, most often an A/AAAA record (pointing the subdomain to an IP address) or a CNAME record (aliasing it to another hostname). Once DNS resolves the subdomain to a destination, the web server or application stack (Apache, Nginx, a reverse proxy, or a platform router) decides how to handle the request.
On the hosting side, subdomains can be mapped in different ways: to a separate document root (a different folder), to a different virtual host, to a different container or application, or even to a completely different hosting account. SSL/TLS must also be considered: each subdomain needs certificate coverage, either via a wildcard certificate (*.example.com) or individual certificates. Cookies and authentication can be shared or isolated depending on how the application sets cookie domains and security policies.
Why It Matters for Web Hosting
Subdomains affect how you structure a site across hosting plans and services. When comparing hosting options, check how many subdomains are allowed, whether each subdomain can have its own document root, and how DNS management is handled. Also consider SSL support (wildcard vs per-host), resource isolation (separate apps or containers), and whether the control panel makes it easy to route subdomains to different environments like staging or separate applications.
Common Use Cases
- Hosting a blog or knowledge base separately (blog.example.com, help.example.com)
- Running a web app alongside a marketing site (app.example.com)
- Creating staging or development environments (staging.example.com)
- Regional or language variants (us.example.com, fr.example.com)
- Separating services like mail, API, or status pages (api.example.com, status.example.com)
Subdomain vs Subdirectory
A subdomain (blog.example.com) is a separate hostname controlled via DNS and typically configured as its own virtual host or application, while a subdirectory (example.com/blog/) is a path under the same hostname handled by the same site configuration. Subdomains are often better for isolating apps, routing to different servers, or using different stacks, whereas subdirectories are simpler to manage under one site and usually share the same SSL certificate and server context by default.