# DNS glossary for custom domains: apex, CNAME, ALIAS

> Plain-language DNS terms behind custom domains: apex domain (zone apex), CNAME and A records, ALIAS flattening, TXT verification, propagation.

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- Site index for agents: https://dodomain.io/llms.txt
- Full documentation as Markdown: https://dodomain.io/docs/llms-full.txt

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Glossary

## The DNS terms behind custom domains

Connecting a customer's domain to a SaaS product touches a handful of DNS ideas that are easy to half-know. Each entry below explains one of them: what it is, what the rules actually say, and what it means for a product that serves customer domains.

- [Apex domain](https://dodomain.io/glossary/apex-domain)
  
  An apex domain is the name at the top of a DNS zone, such as example.com with no label in front of it. It is also called the zone apex, root domain, naked domain or bare domain.
- [CNAME record](https://dodomain.io/glossary/cname-record)
  
  A CNAME (canonical name) record makes one DNS name an alias of another: a resolver that asks for the alias is told the canonical name and continues its lookup there.
- [A record](https://dodomain.io/glossary/a-record)
  
  An A record maps a DNS name to an IPv4 address. Its IPv6 counterpart is the AAAA record. Together they are the records that finally turn a name into somewhere a connection can go.
- [ALIAS record and CNAME flattening](https://dodomain.io/glossary/alias-and-cname-flattening)
  
  ALIAS, ANAME and CNAME flattening are DNS-provider features that let a zone apex point at a hostname: the provider's nameservers resolve the target themselves and answer the apex query with ordinary A and AAAA records.
- [TXT record verification](https://dodomain.io/glossary/txt-record-verification)
  
  TXT record verification proves control of a domain by asking its owner to publish a specific random value in a DNS TXT record, which the verifying service then reads back from the domain's authoritative nameservers.
- [DNS propagation](https://dodomain.io/glossary/dns-propagation)
  
  DNS propagation is the everyday name for the delay between changing a DNS record and every resolver returning the new value. Nothing is pushed anywhere: the delay is caches expiring at the end of the record's TTL.
- [Registrar vs authoritative DNS host](https://dodomain.io/glossary/authoritative-vs-registrar)
  
  The registrar is the company a domain is registered and renewed through; the authoritative DNS host is whoever runs the nameservers the domain is delegated to, which is where its records actually live. They are often, but not always, the same company.
- [Subdomain vs custom domain](https://dodomain.io/glossary/subdomain-vs-custom-domain)
  
  In a SaaS product, a subdomain is an address the vendor issues under its own domain, such as acme.yourproduct.com; a custom domain is an address on the customer's own domain, such as app.acme.com, which the customer points at the product through their DNS.
- [Domain Connect](https://dodomain.io/glossary/domain-connect)
  
  Domain Connect is an open protocol that lets a DNS provider apply a pre-registered template of DNS records to a user's domain after the user approves a single consent screen at the provider, with no manual record entry.

### Check a real domain

The [free DNS tools](https://dodomain.io/tools) run the same checks DoDomain runs when it connects a customer domain: which provider serves the zone, what its authoritative nameservers answer, and whether an SPF record stays inside its lookup limit. The [guides](https://dodomain.io/guides) go further, from multi-tenant custom domains in four frameworks to whether custom domains move conversion.

### Start on the free plan

No card, no sales call: create an app, mint a session, and watch the first domain verify.

[Start with 50 free](https://app.dodomain.io/signin?mode=signup) [Read the quickstart](https://dodomain.io/docs)