Every term you’re likely to meet, explained without jargon. Useful when a supplier is explaining something and you’d rather not have to take their word for it.
A
A record — Points a domain at a server’s IPv4 address. What makes your website load.
AAAA record — The same, for IPv6 addresses.
ALIAS / ANAME record — A provider-specific record behaving like a CNAME but usable at the root of a domain, where a CNAME isn’t permitted.
Authoritative nameserver — The server holding the real, definitive DNS records for a domain, as opposed to a cached copy.
Auth code — See EPP code.
Auto-renew — Automatic renewal before expiry using a stored payment method. Fails silently when the card expires, which is a common cause of lost domains.
C
CAA record — Specifies which certificate authorities are permitted to issue SSL certificates for your domain. A cheap, sensible restriction.
ccTLD — Country-code top-level domain: .uk, .de, .fr. Some, like .io and .ai, are used internationally as branding but remain under their country’s control.
CNAME record — Points one hostname at another hostname rather than at an address.
D
DKIM — DomainKeys Identified Mail. A cryptographic signature on outgoing email, verified against a key published in your DNS, proving the message is genuinely from your domain and unaltered.
DMARC — Tells receiving mail servers what to do when a message fails SPF or DKIM checks, and requests reports on who is sending mail as your domain. The main defence against domain impersonation.
DNS — Domain Name System. Translates domain names into the addresses machines route to.
DNSSEC — Cryptographic signing of DNS records so they can’t be forged in transit. Protects against spoofing and cache poisoning.
Drop catching — Automated registration of a domain the instant it’s deleted and released. Why a valuable expired domain is gone within seconds.
E
EPP code — Also called an auth code or transfer code. A password issued by your current registrar authorising a domain transfer. Not used for .uk domains, which use IPS tags instead.
Expiry date — When a registration ends. Not when the domain becomes unrecoverable — see grace period and redemption period.
G
Glue record — An address record stored at the registry, needed when a domain’s nameservers are within the domain itself. Prevents a circular lookup.
Grace period — A window after expiry during which a domain can still be renewed at normal cost. Length varies by extension and registrar.
gTLD — Generic top-level domain: .com, .org, .net, plus newer ones like .agency.
H–I
Hosting — Where the website itself runs. Distinct from your registrar and your DNS.
HSTS — Instructs browsers to only ever connect to your site over https, preventing downgrade to an insecure connection.
ICANN — The body coordinating the global domain name system and accrediting registrars for generic extensions.
IPS tag — The .uk equivalent of an auth code: a short identifier for the registrar holding a domain. Changing it transfers the domain.
M–N
MX record — Specifies which servers receive email for your domain. The record most often destroyed by accident during website changes.
Nameserver — A server holding DNS records for a domain. Usually at least two, for redundancy.
Nominet — The UK registry, responsible for .uk domains including .co.uk and .org.uk.
NS record — Declares which nameservers are authoritative for a domain.
P–R
Parked domain — A registered domain not currently in use, often showing a placeholder page.
Propagation — The commonly-used term for the delay before a DNS change is visible everywhere. Slightly misleading: nothing spreads outwards; cached copies of the old answer simply expire at different times.
Redemption period — A stage after the grace period when a domain can still be recovered, but with substantial additional fees.
Registrant — The legal owner of a domain. The single most important field on any domain record.
Registrar — The company through which a domain is registered and administered.
Registry — The organisation operating an entire extension. Nominet runs .uk; Verisign runs .com.
Resolver — The server that performs DNS lookups on a user’s behalf, usually run by their internet provider.
Root servers — The top of the DNS hierarchy, directing queries to the right registry.
S
SPF — Sender Policy Framework. A DNS record listing which servers may send email using your domain. A domain may only have one, which is why adding a new tool often accidentally breaks the existing setup.
SRV record — Points to a specific service on a specific port. Used by some telephony and collaboration systems.
SSL / TLS — The encryption behind https and the padlock. SSL is the older name; TLS is what’s actually used. Maximum certificate validity fell to 200 days on 15 March 2026, dropping to 100 days in March 2027 and 47 days in March 2029.
Subdomain — A section in front of your domain: shop.yourcompany.co.uk.
T
TLD — Top-level domain. The part after the final dot.
Transfer lock — A registrar setting preventing a domain being moved without deliberate authorisation. Usually free, frequently switched off.
TTL — Time to live. How long other servers should cache a DNS answer before asking again. Lower it before a planned change to make the switch fast.
TXT record — Free-form text in DNS, used for SPF, DMARC and service verification.
Typosquatting — Registering misspellings of a domain to catch mistyped traffic and email. A common first step in invoice fraud.
U–Z
UDRP — Uniform Domain-Name Dispute-Resolution Policy. The process for challenging a bad-faith registration of a .com-style domain. Nominet runs a separate service for .uk.
WHOIS — The public record of a domain’s registration. Heavily redacted for personal data since GDPR, so it often shows less than people expect.
Wildcard certificate — An SSL certificate covering all subdomains of a domain at once.
Zone file — The complete set of DNS records for a domain.
60-day lock — The period after registration or transfer during which a domain cannot be transferred again. Catches people out when moving suppliers in a hurry.
Still unclear on something?
Ask us — we’d rather explain it than have you nod along. Call 01202 835235 or email contact@domainwarden.co.uk.
See also: how DNS actually works and what happens when a domain expires.