Domain and DNS glossary in plain English

301 redirect (permanent redirect)

A web server’s way of saying “this page has moved for good; go to the new address”. Browsers follow it automatically, and search engines pass the old address’s standing to the new one. 301 and 302 compared.

302 redirect (temporary redirect)

A web server’s way of saying “go over there for now”. Browsers follow it, but search engines keep treating the original address as the real one.

A record

A DNS record that points a name at an IPv4 address, such as 203.0.113.10. It’s the record that sends visitors to your web server. More in DNS records explained.

AAAA record (say “quad-A”)

The same as an A record, but for an IPv6 address.

ABN (Australian Business Number)

An 11-digit number the Australian Business Register issues to a business or other entity. An active ABN is the usual way to show you’re eligible for a .com.au or .net.au, and it’s checked again when the name renews. The ABN check at renewal.

ABR (Australian Business Register)

The Australian Government’s register of ABNs, kept by the Australian Taxation Office. Its public search, ABN Lookup, is where anyone can check whether an ABN is active, and it’s free to use for your own self-check.

ACN (Australian Company Number)

A nine-digit number ASIC (the Australian Securities and Investments Commission) gives every company registered in Australia. A company can use its ACN, or the ABN linked to it, to show it’s eligible for a .com.au.

ALIAS record (ANAME, CNAME flattening)

A workaround some DNS hosts offer so the bare domain can follow another hostname, which a CNAME isn’t allowed to do there. Why a CNAME can’t go on the bare domain.

Alignment (DMARC alignment)

The DMARC test that the domain checked by SPF or DKIM matches the domain in the From address a reader sees. Without it, a message could pass the checks for one domain while claiming to be from another. More.

Apex (bare domain, root domain, naked domain)

Your domain with nothing in front of it: yourname.com.au, not www.yourname.com.au. Most DNS editors write it as @.

APNIC

The Asia Pacific Network Information Centre: the regional body that hands out IP addresses in the Asia/Pacific region, including Australia. Who hands out IP addresses.

ARBN (Australian Registered Body Number)

A nine-digit number ASIC gives a registered body that isn’t an Australian company, such as a foreign company registered to carry on business in Australia. It counts as a commercial entity for a .com.au or .net.au.

auDA (.au Domain Administration)

The not-for-profit organisation that administers the .au domain. It sets the rules for .au names, such as who can register a .com.au, and accredits the registrars that sell them. More in lesson 6.

auDRP (.au Dispute Resolution Policy)

auDA’s process for a dispute between the holder of a .au name and someone who claims rights to it, such as the owner of a matching trade mark, where the name was registered or used in bad faith. An independent panel decides; either side can still go to court.

Australian presence

auDA’s eligibility test for a direct .au name. Australian citizens and permanent residents have one, and so do ABN holders, organisations registered in Australia and Australian trade mark holders; the full list of categories is in auDA’s Licensing Rules. Domains without an ABN.

Auth code (transfer code, EPP code, authInfo, domain password)

The password that proves you’re allowed to move a domain to a different registrar, or to authorise changes to it. You get it from your current provider and give it to the new one. For .au names it’s usually called the domain password. More in the transfers lesson; every route to a .com.au domain password.

Authoritative nameserver

A nameserver that holds a zone’s actual records and gives the final answer, as opposed to a resolver repeating an answer it heard earlier. Who’s involved in a lookup.

Auto-renew

A setting that renews a domain for another term without you doing anything, charging a saved payment method. Worth knowing whether it’s on or off for each domain you hold.

Bounce (bounce message, non-delivery report)

The automatic “this couldn’t be delivered” email you get back when a message can’t reach its destination. It usually says why, which makes it the first thing to read when email goes missing.

Business name (registered business name)

A name you trade under that isn’t your own first name and surname, registered with ASIC (the Australian Securities and Investments Commission). It isn’t exclusive, so similar names can still exist, and registering one doesn’t reserve the matching domain name. What a business name protects.

CAA record

A DNS record that names the certificate authorities allowed to issue SSL certificates for your domain. Optional. More.

Cache (caching)

A stored copy of an answer. Resolvers, devices and browsers all cache DNS answers so they don’t have to look them up every time. How long is set by the record’s TTL. Caching and TTL.

Canonical address

The one web address you’ve chosen as the real one for your site, such as https://www.yourname.com.au. Every other version should redirect to it. Four addresses, one site.

Catch-all address

A setting that accepts email sent to any address at your domain, including ones that don’t exist. Handy for catching typos, and a reliable way to collect spam.

ccTLD (country-code top-level domain)

A two-letter ending for a country or territory, such as .au, .nz or .uk. Each one sets its own rules about who can register.

Certificate authority (CA)

An organisation that browsers trust to issue SSL certificates. Before issuing one, it checks that whoever is asking really controls the domain. How a certificate gets issued.

Chain of trust

How DNSSEC proves an answer is genuine: the root vouches for each ending, each ending vouches for the domains under it, and your zone signs its own records. More.

Change of registrant (CoR, ownership change)

Putting a domain into a different person’s or business’s name. It’s a separate process from moving between registrars, and for .au names the new registrant has to be eligible and the current registrant must still be eligible too. Two kinds of transfer; change of registrant for a .com.au.

CNAME record

A DNS record that makes one name an alias of another name. It can’t share its name with any other record, which is why it can’t go on the bare domain. The CNAME rules.

Commercial entity

auDA’s term for the kinds of body that may hold a .com.au or .net.au: among them a company with an ACN, a business with an ABN, a body with an ARBN, an incorporated association, and the holder or applicant of an Australian trade mark. The full list is in auDA’s Licensing Rules. Domains without an ABN.

Contested name

A direct .au name that more than one eligible holder applied for in the 2022 priority round, for example where yourname.com.au and yourname.net.au were held by different people. If the competing claims rank equally, the name stays on hold until the applicants agree or only one application is left; about 3,000 were still contested in August 2026. More.

Correction (correction of registrant information)

auDA’s process for fixing a genuine error in who is recorded as the registrant of a .au name. Only the registrant on record can ask for it, within 14 days of the licence being recorded. Anything else, such as a sale or a new company, is a change of registrant, and a dead contact email is simply an update. Change of registrant for a .com.au.

Country targeting

How a search engine works out which country a website is for. A country-code ending such as .au is one clear signal; for a .com, Google reads others, such as a local address and phone number, the language and currency on the page, links from local sites and hreflang annotations. .com.au, .au or .com?

Delegation

One zone handing part of the name tree to another set of nameservers, using NS records. The registry delegates your domain to the nameservers you choose. More in lesson 5.

Direct .au (.au direct)

A name registered straight under .au, such as yourname.au, with no com or org in between. Launched in 2022 and open to anyone with an Australian presence; there’s no name-match rule unless you qualify through a trade mark. Do you need the .au as well?

DKIM (DomainKeys Identified Mail)

A way for your mail provider to sign outgoing email so receivers can check it really came from your domain and wasn’t altered. The matching key is published as a TXT record. More.

DMARC

A TXT record at _dmarc that tells receiving mail servers what to do with email that fails the SPF and DKIM checks, and where to send reports. More.

DNS (Domain Name System)

The internet’s directory. It turns a domain name into the records behind it, most often the IP address of a server. How DNS works.

DNS host (DNS hosting, DNS provider)

The company that runs the nameservers holding your zone. It’s where you edit your DNS records. It can be the company you registered the domain with, your web host, or a specialist such as Cloudflare. Three jobs, often three companies.

DNSKEY record

The public key a DNSSEC-signed zone publishes, so resolvers can check the signatures on its records.

DNSSEC (DNS Security Extensions)

An add-on to DNS that signs answers digitally, so a resolver can check they haven’t been forged on the way. DNSSEC explained.

Domain hijacking

Someone taking control of a domain they have no right to, usually by getting into the account it’s managed from and then transferring it away or changing its nameservers. How to stop it.

Domain name

A readable name, such as yourname.com.au, that stands in for the numeric addresses computers use. What is a domain name?

Domain validation (DV)

The basic check behind most SSL certificates: proof that you control the domain, and nothing more. It says nothing about who you are or whether your business is legitimate. Kinds of certificate.

DS record

The record that links a DNSSEC-signed zone to the level above. It’s held at the registry, so you add it where the domain is registered, not in your DNS editor. More.

Eligibility

The rules about who may register a particular ending. A .com.au needs an Australian commercial entity, for example, while a .com is open to anyone. For .au names you must stay eligible the whole time you hold the name, and it’s checked again at renewal. The ABN check at renewal; see also the FAQ.

Email alias

An extra address that delivers into an existing mailbox. sales@ and accounts@ can both be aliases of one person’s inbox. Mailboxes, aliases and forwards.

EPP (Extensible Provisioning Protocol)

The language registrars use to talk to registries. You’ll meet the name in “EPP code”, another word for the auth code, and in the status codes shown on a WHOIS record.

Expiry date

The day a registration period ends. Renew before it and nothing changes. After it, the website and email stop, and following a grace period the name is released for anyone eligible to register. What happens when a domain expires.

Fake renewal notice (false billing, domain slamming)

A letter or email dressed up as a renewal invoice from a company you’ve never dealt with, or a fake page that takes your card details. Paying it buys a different, similar-looking name, moves your domain to them, or simply loses the money. How to spot one; domain renewal scams in Australia.

Forwarding (URL forwarding, email forwarding)

Sending visitors, or email, on to another destination without hosting anything yourself. URL forwarding sends anyone who visits your domain on to another web address. Email forwarding passes mail sent to an address at your domain on to an inbox you already use. More.

FQDN (fully qualified domain name)

A complete name with every part written out, such as www.yourname.com.au, as opposed to just www. Setup guides sometimes ask for one.

Glue record (child nameserver)

A nameserver’s IP address stored at the registry. Only needed when your nameservers are named inside your own domain, such as ns1.yourname.com.au. More.

Google Business Profile

Google’s free listing for a business on Search and Maps, showing its address, hours, reviews and website. It’s one of the signals Google uses to tie a business to a place, whatever its domain ending.

Grace period

The window after a domain expires when the holder can still renew it. For .au names it’s 30 calendar days. For other endings the length depends on the registrar. What happens after expiry.

GST (goods and services tax)

Australia’s 10% tax on most goods and services. auDA quotes the .au wholesale price before GST; the list prices on this site include it.

gTLD (generic top-level domain)

An ending that isn’t tied to a country, such as .com, .net, .org, .dev or .xyz.

Hostname

A full name that leads to one particular server or service, such as www.yourname.com.au or mx1.mailhost.example.

Hosts file

A small file on every computer that overrides DNS for that one machine. Handy for testing, and an occasional cause of “it only happens on my computer”.

hreflang

An annotation in a page’s code, its HTTP headers or a sitemap that tells search engines which language and region the page is written for, so they can show the right version to each visitor. It describes the page, not the domain ending.

HSTS (HTTP Strict Transport Security)

A rule a website gives browsers: only ever connect to me over HTTPS. Some endings, including .dev and .app, have it switched on for every site. More.

HTTPS

The secure way of loading a website. The connection is encrypted, and a certificate proves the site really is the name in the address bar. HTTPS and SSL certificates.

IANA (Internet Assigned Numbers Authority)

The part of ICANN that keeps the internet’s top-level lists. It manages the DNS root zone, which records who runs each ending, and allocates IP address blocks to the regional registries. More in lesson 6.

ICANN (Internet Corporation for Assigned Names and Numbers)

The not-for-profit organisation that coordinates domain names and IP addresses worldwide. It contracts with the registries for endings like .com and accredits their registrars. It doesn’t control what’s on the internet. More in lesson 6.

IDCARE

Australia and New Zealand’s national identity and cyber support service, a not-for-profit that helps people and small businesses whose identity documents, card details or accounts have been exposed or misused. Its help for individuals is free.

IMAP

The way mail apps read a mailbox that lives at your mail provider. Because the mail stays on the server, your phone and laptop both see the same inbox.

IP address

The number that identifies a device or server on a network, so data knows where to go. What is an IP address?

IPv4

The older, shorter kind of IP address: four numbers separated by dots, like 203.0.113.10.

IPv6

The newer, much longer kind of IP address, written with colons, like 2001:db8::10. It exists because IPv4 ran short of addresses.

Let’s Encrypt

A not-for-profit certificate authority that issues SSL certificates at no charge and automatically. Most web hosts use it behind the scenes. More.

Licence

What you actually hold when you register a .au domain: the right to use the name for a set period. You don’t own it outright. More in lesson 1.

Licence period

How long a .au licence runs for: one to five years, chosen when you register or renew. A change of registrant starts a new licence period for the new holder, and whole years left on the old one carry over. Change of registrant for a .com.au.

Mailbox

Somewhere email is actually stored, with a login, an inbox and a sent folder. It lives at a mail provider, not at your domain registrar. Mailboxes, aliases and forwards.

MX record (mail exchanger)

A DNS record that names the servers accepting email for your domain. Lower priority numbers are tried first. More.

Nameserver (name server, DNS server)

A server that publishes a zone and answers questions about it. Your domain is delegated to at least two, and whoever runs them is where your live DNS records are kept. Nameservers and DNS zones.

Namespace

auDA’s word for an ending within .au, such as com.au, org.au, id.au or direct .au. Each namespace has its own eligibility rules.

NS record

A DNS record naming the nameservers in charge of a zone. They exist at the registry and inside your own zone, and the two lists should match. Why both matter.

Null MX

A special MX record that says “this domain doesn’t accept email at all”. Useful on a domain you only hold to protect a name. Domains that don’t send email.

Parked domain

A domain that’s registered but not in use yet. It usually shows a simple holding page.

Passkey

A way of signing in with your device’s fingerprint, face or PIN, with no password to steal or reuse. It only works on the real site, which makes it very hard to phish.

Pending delete

The last stage for an expired .com or similar name: it can no longer be renewed or restored, and in a few days it will be released for anyone to register. What happens after expiry.

Phishing

A message that pretends to be from a company you trust, to get you to sign in on a fake page or pay a fake invoice. More.

Priority allocation

The process auDA ran when direct .au names launched. From 24 March to 20 September 2022 (UTC), whoever already held the matching .com.au, .net.au or other .au name could apply for the .au before anyone else. The window is closed, unclaimed names are first come, first served, and some contested names are still on hold. What happened to priority allocation?

Private address

An IP address that only works inside one home or office network, such as anything starting with 192.168.. The public internet can’t reach it. Public and private addresses.

Propagation

The wait after a DNS change before everyone sees it. Nothing is really spreading: old cached answers are expiring, each on its own timer. Why changes take time.

QPI (Quality Performance Index)

auDA’s Quality Performance Index Program, which from 1 October 2026 gives a rebate to accredited registrars that meet its quality, compliance and security criteria. It goes to registrars, not to domain holders. Not to be confused with the unrelated Quality Performance Index that Public Interest Registry introduced for .org in 2019. The October 2026 .au price rise.

RDAP (Registration Data Access Protocol)

The modern replacement for WHOIS. It gives the same kind of registration details in a standard, structured format. WHOIS and RDAP.

Record (DNS record, resource record)

One instruction in a zone: a name, a type, a value and a TTL. DNS records explained.

Redemption period (redemption grace period)

For .com and similar endings, the 30 days after an expired name is deleted during which the old holder can still get it back, usually for a sizeable fee. .au names don’t have this stage. What happens after expiry.

Redirect

A web server telling a browser “the page you asked for is at this other address”. It’s done by a server, not by DNS. What a redirect is.

Registrant

The person or organisation a domain is registered to. That should be you or your business, not your web designer. More in lesson 6.

Registrant contact

The person, and email address, that a .au registrant nominates to deal with the domain. The domain password and transfer confirmations go to this address, so keep it current, ideally at a mailbox that isn’t on the same domain. Registrant or registrant contact: whose inbox is it?

Registrar

A company accredited to add and change names in a registry. Its name appears on the domain’s public WHOIS record. More in lesson 6.

Registrar lock (transfer lock)

A setting that blocks a domain from being transferred to another registrar until you switch it off. A sensible default for any domain you rely on. Locks.

Registry

The single master list of every name under one ending, and the organisation that keeps it. For .au, auDA is in charge and Identity Digital Australia operates it. For .com it’s Verisign. More in lesson 6.

Registry operator

The company that runs a registry’s systems day to day. For .au that’s Identity Digital Australia, under contract to auDA.

Registry search (registry search request)

A request to auDA to list every .au licence issued using your details, such as your company name, ABN, ACN or trade mark. Useful when a business is sold or wound up and nobody is sure which names it holds; auDA asks for proof that you’re entitled to the information.

Renewal

Paying for another term so you keep the name. For .au that’s usually done before the licence expires, but auDA also allows renewal in a 30-day grace period after expiry. Renewal and expiry.

ReportCyber

The Australian Government’s online form for reporting cybercrime to police, run by the Australian Cyber Security Centre at cyber.gov.au. Use it if a scam cost you money or someone got into an account, and report the scam itself to Scamwatch as well.

Reseller

A business that sells and supports domains through an accredited registrar, without being a registrar itself. Chill Domains is a reseller. More in lesson 6.

Resolver (recursive resolver, DNS resolver)

The server that does DNS lookups on your behalf and remembers the answers. Usually run by your internet provider, or a public service. One lookup, step by step.

Root zone (the root, root servers)

The very top of the DNS, written as a single dot. It lists who runs each ending. The root servers that publish it are a network of hundreds of machines under 13 names. More.

RRSIG record

A DNSSEC signature. Each set of records in a signed zone comes with one, and a resolver checks it against the zone’s DNSKEY.

Scamwatch

The Australian Government’s scam reporting and alerts service at scamwatch.gov.au, run by the National Anti-Scam Centre within the ACCC (Australian Competition and Consumer Commission). Report a fake domain renewal notice there whether or not you paid. Domain renewal scams in Australia.

Second-level domain (2LD)

The part directly to the left of the top-level domain. In yourname.com that’s your name. In .au, com.au, net.au, org.au and id.au are second-level namespaces, and your name sits inside one of them. More.

Selector (DKIM selector)

The label that tells a receiving mail server which DKIM key to look up. It’s the first part of the record’s name, before ._domainkey, and your mail provider chooses it.

SMTP

The protocol mail servers use to hand email to each other, and that your mail app uses to send. Reading mail is a different job, done by IMAP.

SOA record (start of authority)

A zone’s housekeeping record: one per zone, created and maintained by your DNS host. You can leave it alone.

SPF (Sender Policy Framework)

A single TXT record, starting v=spf1, listing the servers allowed to send email for your domain. A domain must have only one. More.

Split DNS (split-horizon DNS, internal DNS)

When an office’s own DNS server gives different answers from the public DNS for the same name. A common reason a site works from home but not from the office. More.

Spoofing

Sending email with a forged From address so it appears to come from someone else’s domain. SPF, DKIM and DMARC exist to let receivers catch it.

SRV record

A DNS record that points a particular service at a server and a port number. Used by some phone, chat and office systems.

SSL certificate (TLS certificate)

A file on your web server that proves the site is really yours and lets the connection be encrypted, giving you the padlock and https://. It’s issued for a domain name, but it’s a separate thing from the domain, and it usually comes from your web host. HTTPS and SSL certificates.

Status code (EPP status code)

A label on a domain’s public record that says what state it’s in, such as ok, clientTransferProhibited (locked), serverHold (switched off by the registry) or serverRenewProhibited (the registry won’t allow a renewal). The codes you’ll see.

Subdomain

Anything in front of your registered name, such as shop.yourname.com.au. You create subdomains yourself by adding DNS records. More.

Suspension (suspended licence)

What happens to a .au licence when the registrant no longer meets auDA’s rules, for instance because the ABN behind it has been cancelled, or when the registrant’s details aren’t updated in time. A suspended name stops resolving and can’t be transferred, and the licence is cancelled if the problem isn’t fixed within 30 days.

TLD (top-level domain, extension)

The last part of a domain name: .au, .com, .org. People also call the whole ending, such as .com.au, the extension.

TLS (Transport Layer Security)

The technology that actually does the encrypting behind HTTPS. It replaced SSL years ago, but the old name stuck, which is why people still say “SSL certificate”.

Trade mark (registered trade mark)

A brand registered with IP Australia for chosen classes of goods or services. It’s the only registration that gives exclusive rights to use the brand in Australia, and it lasts 10 years from the filing date before it needs renewing. Holding or having applied for an Australian trade mark is also one way to be eligible for a .com.au, .net.au or direct .au name. When a trade mark is worth it.

Transfer

Moving a domain from one registrar to another. The name and the registrant stay the same. You need the auth code. Transfers, locks and status codes.

Trust anchor

The one key a DNSSEC-checking resolver has to know in advance: the root zone’s. Everything else is verified by following the chain down from it.

TTL (time to live)

The number of seconds an answer may be reused before it has to be looked up again. 3600 is one hour. Caching and TTL.

Two-factor authentication (2FA, two-step verification)

A second proof at sign-in, usually a six-digit code from an app on your phone. Someone who steals your password still can’t get in without it.

TXT record

A DNS record that holds a line of text for other systems to read. Used for SPF, DKIM, DMARC and “prove you control this domain” checks. More.

Typosquatting (lookalike domain)

Registering a name that looks like someone else’s, such as a misspelling or a different ending, to catch their visitors or imitate them by email. More.

URL (web address)

The full address of one page: how to connect, which name and which page, as in https://www.yourname.com.au/menu. The domain name is the middle part.

Validating resolver

A resolver that checks DNSSEC signatures and refuses any answer that fails. If nobody along the way validates, DNSSEC signatures go unchecked.

WHOIS

The public lookup that shows whether a domain is registered and through which registrar. How much it shows about the registrant depends on the ending. WHOIS, RDAP and privacy.

WHOIS privacy (ID protection)

A service that keeps your contact details out of public WHOIS results. It’s available on many endings, but not allowed for .au names. More.

Wholesale price

The price a registry charges registrars for each name, before the registrar or reseller adds its own margin. For .au names auDA sets it and quotes it before GST; it rose from $8.64 to $9.50 a year on 1 October 2026. The October 2026 .au price rise.

Wildcard certificate

An SSL certificate that covers every subdomain at one level, written *.yourname.com.au. One certificate then serves shop, blog and anything else you add.

Wildcard record

A record written with * that answers for any subdomain without records of its own. More.

www

Just a subdomain that became a habit. www.yourname.com.au and yourname.com.au are separate names, and each needs its own record. www or not?

Zone (DNS zone)

One part of the DNS, managed in one place. Your domain’s zone is its full set of records, kept at your DNS host. Several providers can hold a zone for the same domain, but only one is live. Which zone is live?

Zone file

A zone written out as a plain text file. Some DNS hosts let you export or import one, which makes moving providers easier.

Domain and DNS glossary, in plain English

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