DNSname

DNSname, commonly referred to as a DNS name, is a name used in the Domain Name System to identify a resource such as a computer, service, or endpoint on a network. DNS names are hierarchical and written as a sequence of labels separated by dots, from the root at the far right to the most specific label on the left. The fully qualified domain name (FQDN) specifies the exact path to a resource, for example www.example.com. The root label is implicit; some notations include a trailing dot to indicate the root.

In common usage, the host name is the leftmost label, the domain name is the portion of the FQDN that refers to the registered domain, and the DNS name is the complete FQDN. However, terms are often used interchangeably.

Technical rules: DNS names are case-insensitive; labels may contain letters A–Z, digits 0–9, and hyphens; labels must not start or end with a hyphen. Each label is limited to 63 characters; the full FQDN is limited to 253 characters. Internationalized domain names are allowed via punycode.

Resolution and usage: Clients query DNS servers to translate a DNS name into an IP address or retrieve records such as MX, CNAME, or SRV. DNS names are used in URLs, email addresses, TLS certificates, and service discovery on public and private networks. DNSSEC adds data integrity and authenticity, while DNS over TLS or DNS over HTTPS helps protect queries. See also FQDN, hostname, domain name, IDN, DNSSEC.