DNS Record Types Explained: A, AAAA, CNAME, MX, TXT, NS, SOA

Every domain on the internet relies on DNS records to function. These records are instructions stored on authoritative nameservers that tell the rest of the internet how to find your website, where to deliver your email, and how to verify your domain's identity.

There are dozens of DNS record types defined in various RFCs, but most domains use fewer than ten. This guide covers the seven record types you will encounter most often, with practical examples and guidance on when to use each one.

A Record

The A record is the most fundamental DNS record type. It maps a domain name to an IPv4 address.

When someone types example.com into a browser, the DNS resolver ultimately needs an IP address to connect to. The A record provides that mapping.

example.com.    300    IN    A    93.184.216.34

When to use A records

• Pointing your root domain (example.com) to a web server
• Pointing subdomains (api.example.com) to specific servers
• Any situation where you need a domain to resolve to a specific IPv4 address

Key considerations

A records can only point to IPv4 addresses. You can have multiple A records for the same domain, which is a basic form of load balancing called DNS round-robin. The resolver will return all records, and the client chooses one.

AAAA Record

The AAAA record is the IPv6 equivalent of the A record. It maps a domain name to an IPv6 address.

example.com.    300    IN    AAAA    2606:2800:220:1:248:1893:25c8:1946

The name "AAAA" (quad-A) reflects that IPv6 addresses are four times the size of IPv4 addresses (128 bits vs 32 bits). As IPv6 adoption grows, AAAA records become increasingly important.

When to use AAAA records

• Whenever your server supports IPv6 (which it should)
• Alongside A records for dual-stack connectivity
• Required for IPv6-only networks, which are becoming more common on mobile carriers

Most modern configurations include both A and AAAA records. Clients that support IPv6 will prefer the AAAA record, while older clients fall back to the A record.

CNAME Record

A CNAME (Canonical Name) record creates an alias from one domain name to another. Instead of pointing to an IP address, it points to another hostname.

www.example.com.    300    IN    CNAME    example.com.
blog.example.com.   300    IN    CNAME    hosting-provider.com.

When a resolver encounters a CNAME, it follows the chain and resolves the target hostname to get the final IP address.

When to use CNAME records

• Pointing www to your root domain
• Pointing subdomains to third-party services (CDNs, SaaS platforms, hosting providers)
• Domain verification for services like Google Workspace or AWS Certificate Manager

Critical restrictions

CNAME records have a rule that trips up many administrators: a CNAME cannot coexist with any other record type at the same name. This means you cannot put a CNAME on your root domain (example.com) if you also have MX records there, which you almost certainly do.

MX Record

MX (Mail Exchange) records specify which mail servers handle email for a domain. Without correct MX records, email sent to your domain will not be delivered.

example.com.    300    IN    MX    10 mail1.example.com.
example.com.    300    IN    MX    20 mail2.example.com.

The number before the mail server hostname is the priority value. Lower numbers indicate higher priority. In the example above, mail is delivered to mail1.example.com first. If that server is unavailable, the sending server tries mail2.example.com.

When to use MX records

• Routing email to your mail server or email hosting provider
• Setting up Google Workspace, Microsoft 365, or any email service
• Configuring backup mail servers with different priority values

Key considerations

MX records must point to a hostname, not an IP address. That hostname must have its own A or AAAA record. An MX record should never point to a CNAME.

TXT Record

TXT records hold arbitrary text data associated with a domain. Originally designed for human-readable notes, they now serve critical roles in email authentication and domain verification.

example.com.    300    IN    TXT    "v=spf1 include:_spf.google.com ~all"
example.com.    300    IN    TXT    "google-site-verification=abc123..."

Common uses for TXT records

TXT records have a 255-character limit per string, but you can concatenate multiple strings within a single record for longer values.

NS Record

NS (Name Server) records delegate a domain or subdomain to a set of authoritative nameservers. These records are fundamental to how DNS delegation works.

example.com.    86400    IN    NS    ns1.dnsprovider.com.
example.com.    86400    IN    NS    ns2.dnsprovider.com.

When NS records matter

NS records at the root of your domain are set at the registrar level and determine which DNS provider controls your zone. Changing these records is how you migrate DNS providers.

You can also use NS records to delegate subdomains to different nameservers. For example, a company might delegate staging.example.com to a separate DNS provider used by their development team.

Key considerations

You should always have at least two NS records for redundancy. Most providers give you two to four nameservers. If all nameservers become unreachable, your entire domain becomes unresolvable.

SOA Record

The SOA (Start of Authority) record contains administrative information about the DNS zone. Every zone must have exactly one SOA record.

example.com.    86400    IN    SOA    ns1.dnsprovider.com. admin.example.com. (
    2024010101    ; serial number
    3600          ; refresh
    900           ; retry
    1209600       ; expire
    300           ; minimum TTL
)

SOA record fields explained

• Primary nameserver: The main authoritative nameserver for the zone
• Admin email: The responsible person's email (the @ is replaced with a .)
• Serial number: Incremented with each zone change; used by secondary servers to detect updates
• Refresh: How often secondary servers check for updates
• Retry: How long to wait before retrying a failed refresh
• Expire: How long secondary servers serve data without a successful refresh
• Minimum TTL: The default TTL for negative caching (NXDOMAIN responses)

Most DNS administrators rarely edit SOA records directly since managed DNS providers handle them automatically. But understanding the SOA is useful when troubleshooting zone transfer issues or negative caching behavior.

How Records Work Together

DNS record types do not exist in isolation. A typical domain uses several types simultaneously.

Choosing the Right Record Type

Understanding DNS record types is the foundation for managing any domain reliably. Each record type serves a specific purpose, and misconfiguring even one can break email delivery, take a website offline, or leave a domain vulnerable to impersonation.