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Domain

In short: A human-readable name (e.g. emzett-digital.com) that stands in for a numeric IP address on the internet.

In more detail: Domains are hierarchically structured and resolved into IP addresses via DNS. A domain consists of several parts (labels) separated by dots, becoming more specific from right to left — from the TLD through the second-level domain to optional subdomains.

In Depth

Structure as an address tree

A complete domain reads from right to left like an address tree, with each level managed by its own, independent authority. In shop.emzett-digital.com, .com is the top-level domain, emzett-digital the second-level domain, and shop a subdomain of it:

shop  .  emzett-digital  .  com
 ^         ^                ^
Subdomain  Second-level     Top-level domain

Management of the .com TLD lies with the registry Verisign (which runs the central registration service for all .com domains), the specific domain emzett-digital.com is registered to its owner via a registrar (e.g. Namecheap, IONOS, Cloudflare Registrar), and the owner can create subdomains themselves as they like, without having to ask any external authority for that — this is why companies can freely put shop., api., blog. or staging. in front of their domain, without paying extra or registering anything for it.

Registration and ownership

A domain isn’t “bought”, but rented for a limited period (usually 1-10 years) and has to be renewed — if you miss the renewal, it becomes available again after a grace period and can be registered by someone else. The WHOIS database (often only viewable in a restricted way since the GDPR) shows who registered a domain, when it expires, and which registrar manages it. An important security detail: domain hijacking (the unauthorised transfer of a domain to another registrar or owner) is usually prevented via a combination of domain lock (prevents transfers without explicit approval) and an auth code (a secret code needed for a transfer).

Technically just a name

A domain itself is initially just a string with no technical meaning — only a matching DNS record (typically an A or AAAA record) links it to a real IP address. Without this record, the domain is registered and belongs to someone, but “empty” — it points to nothing, and a browser gets an NXDOMAIN or timeout error when trying to access it.

Character set and internationalisation

Domain names are case-insensitive (capitalisation doesn’t matter) and, since the introduction of IDN (Internationalized Domain Names), may also contain umlauts/special characters — technically, these are internally translated into an ASCII-compatible form called Punycode (emzett-öl.de, for example, becomes xn--emzett-l-x6a.de). Historically, the character set was limited to ASCII letters, digits, and hyphens (defined in RFC 1035) — a lingering effect of this is that many systems (including Emzett’s own slug generation for wiki URLs) voluntarily stick to this convention, even where it’s technically no longer strictly necessary, because it’s universally compatible and works without special-character encoding.

A domain isn’t the same as a URL — the URL additionally contains a protocol (https://), optionally a port, a path, and query parameters, while the domain is just the name part in between. Likewise, a domain isn’t a hostname in the strict sense: a hostname specifically refers to a single machine/server, while a domain, as an overarching naming system, can encompass several hostnames (via subdomains).

See also: TLD, Second-Level Domain, Subdomain, Root Domain

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