Parts of a Domain Name
How a Domain Name Is Structured
The parts of a domain name are its labels, the words separated by dots. They are read from right to left, from the most general level to the most specific. In blog.example.com, there are three labels, and each one has a specific role.
The rightmost label is the top-level domain (TLD), such as com. It is the extension, and what a top-level domain is is explained separately. The next label, example, is the second-level domain. This is the name the owner chose and registered. The leftmost label, blog, is a subdomain that the owner created underneath it.
Some countries use a fixed second-level label for certain types of organization. In example.co.uk, the label co is a category set by the registry, and the name the owner registered is example, placed just before it.
Behind the TLD is the root of the system, which is usually left unwritten. A fully written name ends with a dot, as in example.com., to show that the hierarchy is complete.
Apex Domain vs www: Why the Difference Matters
The apex domain, also called the bare domain, is the registered name with nothing in front of it, such as example.com. Adding www creates a subdomain, so www.example.com is a separate name in the system, even though it is usually set up to show the same site.
The www label is a long-standing convention rather than a requirement. Many sites answer at both addresses, and some send visitors from one to the other. What matters most is consistency: a site should choose one main address and use it throughout. Subdomains in general are described in the subdomain guide.
Frequently asked questions
What Is the Difference Between a TLD and a Domain?
A TLD is the last label of a name, such as com or org. A domain is the full name that someone registers, such as example.com, which combines a second-level name with a TLD. Many domains share the same TLD, but each registered domain belongs to one registration. For the basics, see what a domain name is.
Can a Domain Name Have More Than Two Parts?
Yes. A name such as shop.store.example.co.uk has several labels, and each label to the left adds a level of detail. The owner of a domain can create subdomains beneath it without registering anything new, so the number of labels grows as the site grows. The technical limits are generous. The practical limit is readability, since very long names are harder to read, type and share.