Domain name glossary: A to Z

A plain-English glossary of domain name terms from A records and auth codes to UDRP and WHOIS, with links to full guides.

Every domain term you're likely to run into, explained in one or two plain-English sentences, with links to the full guides.

A B C D E G H I L M N P R S T U W

A

A record

A DNS record that points a domain to an IPv4 address. Learn more

ACPA

The US Anticybersquatting Consumer Protection Act, which lets trademark owners sue cybersquatters in court. Learn more

Aftermarket

The resale market for domains that are already registered. Learn more

Afternic

A large domain marketplace owned by GoDaddy that shows buy-now listings across many registrars. Learn more

Apex domain

The root of a domain without any subdomain, like example.com. Learn more

Auth code

A secret code (also EPP code) needed to transfer a domain to another registrar. Learn more

Auto-renew

A setting that renews your domain automatically before it expires. Learn more

B

Backorder

A request to try to register a domain the moment it becomes available. Learn more

BIN

Buy It Now: a fixed price for a domain. Learn more

Brandable

An invented or creative name that works well as a brand. Learn more

C

ccTLD

A two-letter country code ending, like .uk or .us. Learn more

CNAME

A DNS record that makes one name an alias of another. Learn more

Comps

Comparable sales used to estimate a domain's value. Learn more

Cybersquatting

Registering a domain that copies someone else's trademark in bad faith. Learn more

D

DKIM

An email authentication method that adds a digital signature to messages. Learn more

DMARC

An email policy telling inboxes what to do with mail that fails SPF or DKIM. Learn more

DNS

The Domain Name System, which turns domain names into IP addresses. Learn more

DNSSEC

Security extensions that let DNS answers be verified as genuine. Learn more

Domain hack

A domain where the ending completes the word, like del.icio.us. Learn more

Domaining

Investing in domain names to sell, lease or develop. Learn more

Drop

When an expired domain is deleted and released for anyone to register. Learn more

Drop catching

Using automated services to register domains the instant they drop. Learn more

E

EMD

Exact-match domain: a domain that exactly matches a search phrase. Learn more

End user

A business or person who wants a domain to use, not resell. Learn more

EPP

The protocol registrars use to talk to registries. Learn more

Escrow

A trusted middleman that holds payment until the domain transfer completes. Learn more

G

gccTLD

A country code that Google treats as global, like .io or .ai. Learn more

gTLD

A generic top-level domain not tied to a country, like .com. Learn more

H

Hand reg

A domain you registered new at the standard price. Learn more

I

IANA

The Internet Assigned Numbers Authority, which manages the root zone of the domain system. Learn more

ICANN

The non-profit that coordinates the domain name system and sets rules for generic endings. Learn more

IDN

An internationalized domain name using non-English characters. Learn more

L

Lease-to-own

Paying for a domain in monthly installments, owning it at the end. Learn more

LLL / LLLL

Three-letter or four-letter domains. Learn more

M

MX record

A DNS record that says which servers receive a domain's email. Learn more

N

Nameserver

A server that holds a domain's DNS records. Learn more

New gTLD

One of the hundreds of endings added since 2013, like .app or .shop. Learn more

NNN / NNNN

Three-number or four-number domains. Learn more

P

Parking

Showing ads on an unused domain. Learn more

Pending delete

The final few days before an expired domain is released. Learn more

Premium domain

A name a registry or owner prices above the standard rate. Learn more

Punycode

The ASCII version of an IDN, starting with xn--. Learn more

Push

Moving a domain between accounts at the same registrar. Learn more

R

RDAP

The modern replacement for WHOIS, returning structured registration data. Learn more

RDNH

Reverse domain name hijacking: a bad-faith attempt to take a domain through a dispute. Learn more

Redemption period

A 30-day window after deletion when the owner can still restore a domain for a fee. Learn more

Registrant

The person or company that registered a domain. Learn more

Registrar

A company that sells domains to the public. Learn more

Registrar lock

A setting that blocks unauthorized transfers. Learn more

Registry

The organization that runs the database for a domain ending. Learn more

Registry lock

An extra security layer requiring manual verification before changes. Learn more

Root zone

The top of the DNS hierarchy listing every top-level domain. Learn more

S

Sell-through rate

The share of a portfolio that sells in a year. Learn more

SLD

Second-level domain: the part before the ending, like 'example' in example.com. Learn more

SPF

A DNS record listing which services may send email for a domain. Learn more

sTLD

A sponsored top-level domain for a specific community, like .edu. Learn more

Subdomain

A prefix added to a domain, like shop.example.com. Learn more

T

TLD

Top-level domain: the ending after the last dot. Learn more

TTL

Time to live: how long DNS answers are cached. Learn more

Type-in traffic

Visitors who type a domain straight into the address bar. Learn more

Typosquatting

Registering misspellings of other people's brands. Learn more

U

UDRP

ICANN's process for resolving trademark disputes over domains. Learn more

URS

Uniform Rapid Suspension: a fast dispute process for clear-cut cases in new gTLDs. Learn more

W

WHOIS

The traditional lookup for domain registration details, now replaced by RDAP. Learn more