The SLD (Second-Level Domain) is the part of a domain name that appears directly to the left of the Top-Level Domain (TLD).
In the domain
👉 example.com
.com
is the TLD (Top-Level Domain)
example
is the SLD (Second-Level Domain)
Level | Example |
---|---|
Top-Level Domain | .com |
Second-Level Domain | example |
Subdomain (optional) | www. or e.g. blog. |
Domain | SLD | TLD |
---|---|---|
google.de |
google |
.de |
wikipedia.org |
wikipedia |
.org |
meinshop.example.com |
example |
.com |
The SLD is usually the custom, chosen part of the domain—often representing a company name, brand, or project. It's the most recognizable and memorable part of a domain name.
The Fully Qualified Domain Name (FQDN) is the complete and unique name of a computer or host on the internet or a local network. It consists of multiple parts that reflect a hierarchical structure.
An FQDN is made up of three main components:
Hostname – The specific name of a computer or service (e.g., www
).
Domain Name – The name of the higher-level domain (e.g., example
).
Top-Level Domain (TLD) – The highest level of the domain structure (e.g., .com
).
Example of an FQDN:
👉 www.example.com.
www
→ Hostname
example
→ Domain name
.com
→ Top-Level Domain
The trailing dot (.
) is optional and represents the root domain of the DNS system.
✅ Uniqueness: Each FQDN is globally unique and refers to a specific resource on the internet.
✅ DNS Resolution: It is used by DNS servers to find the IP address of websites and servers.
✅ SSL Certificates: An FQDN is often required for SSL/TLS certificates to ensure secure connections.
✅ Email Delivery: Mail servers use FQDNs to send emails to the correct hosts.
FQDN: mail.google.com
(fully specified)
Simple Domain: google.com
(can contain multiple hosts, e.g., www
, mail
, ftp
)
In summary, the FQDN is the complete address of a device or service on the internet, while a simple domain is a more general address.