A subdomain refers to a domain that’s subdivided into further domains. As seen with the domain, www.example.com, the second-level domain, example, constitutes a subdomain for the top-level domain, .com. Following this pattern, the third-level domain, www., makes up a subdomain for the second-level domain, example.
Regarding a site’s website structure, however, subdomains refer to third-level domains. When, for example, a user wishes to set up an e-commerce platform under the domain, www.example.com, the subdomain, shop.example.com, can be chosen.
Some popular subdomains include:
- mail./smtp./pop3./imap. (Mailserver)
- en./es./fr. (for language-specific websites)
- m. (optimized for mobile devices)
Manually setting up a subdomain is, for the most part, a complex task. There are plugins for implementing subdomains for many content management systems (including names like WordPress, Joomla!, and TYPO3, but these settings also have to be carried on the webserver; wildcards also need to be set up for this. These steps alone are enough to deter many non-experts. Some web hosting services, however, offer support or easier setups processes for subdomains.
Subdomains are especially useful when:
- Content is to be offered in different languages (en.example.com for English and es.example.com for Spanish)
- There are many different topics on a site, but a common theme still exists (flightprices.example.com vs. busprices.example.com)
- Different products are to be highlighted (producer1.example.com, producer2.example.com)