DNS and Domain ToolsDNS record types explained
A DNS record is one line in a domain's address book. The type says what kind of information it holds.
The common types
| Type | What it holds | Example use |
|---|---|---|
| A | An IPv4 address | example.com points to a server |
| AAAA | An IPv6 address | The same server on IPv6 |
| CNAME | Another name (an alias) | www is an alias of username.github.io |
| MX | A mail server and a priority | Where email for the domain is delivered |
| NS | The name servers of the domain | Which servers answer for it |
| TXT | Text | Site verification, SPF, DKIM and DMARC records |
| SOA | The start of authority: zone settings | Serial number and timers |
| CAA | Which certificate authorities may issue certificates | Limits who can make HTTPS certificates |
These types were defined in RFC 1035, the basic DNS specification (CAA and AAAA came later).
Rules that surprise people
- A CNAME stands alone. A name that has a CNAME should not have other records, and so a CNAME cannot be used at the root of a domain (
example.com), where NS and SOA records must exist. Providers offer ALIAS or ANAME records as a workaround. - MX points to a name, not to an address. And that name needs its own A or AAAA record.
- TXT is for anything. Long values are split into pieces of up to 255 characters, which the lookup tool joins for you.
- Several records of one type are normal. Several A records give several addresses, and several MX records give backups.
Try it
Use the DNS lookup page: github.com for A, NS and MX, and _dmarc.google.com for a TXT record.
What is the difference between A and CNAME?
An A record gives an address. A CNAME says "ask for this other name instead".
Where do I change records?
At whoever runs the DNS of your domain, which is the company named in the name server records. It is often the registrar, but not always.
Sources
- RFC 1035: Domain names - implementation and specification (rfc-editor.org/rfc/rfc1035)
- GitHub Docs: Managing a custom domain for your GitHub Pages site (docs.github.com)
Read on 14 November 2026.
This is an independent guide. It is not connected with Cloudflare, Google, ICANN, IANA, GitHub or any registry named here. Facts were read on 14 November 2026 from the documents named on each page. Lookups are made from your browser to the services named in the result.