Glossary · 4 min read

DNS Record Types: A Complete Reference Guide

A technical reference for all major DNS record types including A, AAAA, MX, CNAME, TXT, NS, SOA, PTR, SRV, and CAA. Includes example values and use cases.

DNS Record Types: A Complete Reference Guide

DNS records are the instructions stored in authoritative name servers that tell the internet how to handle requests for a domain. Each record type serves a specific purpose. This reference covers the record types you are most likely to encounter when managing domains, email infrastructure, and web services.

A Record

The Address record maps a hostname to an IPv4 address.

  • Example: example.com. 3600 IN A 93.184.216.34
  • Use: Points your domain or subdomain to a web server. Most domains have at least one A record.

AAAA Record

The IPv6 Address record maps a hostname to an IPv6 address.

  • Example: example.com. 3600 IN AAAA 2606:2800:220:1:248:1893:25c8:1946
  • Use: Same as the A record but for IPv6. As IPv6 adoption grows, publishing AAAA records alongside A records ensures reachability for all clients.

MX Record

The Mail Exchanger record specifies which servers accept email for a domain.

  • Example: example.com. 3600 IN MX 10 mail.example.com.
  • Use: Email delivery depends on MX records. The numeric priority value (10 in the example) determines preference; lower numbers have higher priority. A domain can have multiple MX records for redundancy. Verify yours with our MX lookup tool.

CNAME Record

The Canonical Name record creates an alias from one hostname to another.

  • Example: www.example.com. 3600 IN CNAME example.com.
  • Use: Commonly used to point subdomains like www to the root domain, or to point service-specific subdomains to provider hostnames (e.g., selector1._domainkey.example.com CNAME selector1-example-com._domainkey.provider.com for DKIM). A CNAME cannot coexist with other record types at the same name, and must not be placed at the zone apex (RFC 1034).

TXT Record

The Text record holds arbitrary text data associated with a hostname.

  • Example: example.com. 3600 IN TXT "v=spf1 include:_spf.google.com ~all"
  • Use: TXT records are critical for email authentication. SPF policies, DKIM public keys, and DMARC policies are all published as TXT records. They are also used for domain verification (Google Search Console, Microsoft 365) and other purposes. A domain can have multiple TXT records.

NS Record

The Name Server record delegates a domain or subdomain to a set of authoritative name servers.

  • Example: example.com. 86400 IN NS ns1.cloudflare.com.
  • Use: NS records at the zone apex define which name servers are authoritative for the entire domain. NS records on subdomains can delegate zones (e.g., delegating sub.example.com to different name servers). Check delegation with our DNS lookup tool.

SOA Record

The Start of Authority record contains administrative information about a DNS zone.

  • Example: example.com. 86400 IN SOA ns1.example.com. admin.example.com. 2024010101 3600 900 1209600 86400
  • Use: Every DNS zone has exactly one SOA record. It specifies the primary name server, the responsible party's email (encoded as a hostname), serial number, and timing parameters for zone transfers and caching of negative responses (NXDOMAIN). The serial number must increment with each zone change.

PTR Record

The Pointer record maps an IP address to a hostname, enabling reverse DNS lookups.

  • Example: 34.216.184.93.in-addr.arpa. 3600 IN PTR mail.example.com.
  • Use: PTR records are essential for email servers. Many receiving mail servers (including Gmail and Outlook) verify that a sending IP has a PTR record matching the server's hostname. Missing or mismatched PTR records can cause email rejection. Check your sending IP's reverse DNS with our IP reputation tool.

SRV Record

The Service record specifies the host and port for specific services.

  • Example: _sip._tcp.example.com. 3600 IN SRV 10 5 5060 sipserver.example.com.
  • Use: SRV records are used by protocols like SIP (VoIP), XMPP (messaging), and LDAP. The record includes priority, weight, port, and target host. Format: _service._protocol.name TTL IN SRV priority weight port target.

CAA Record

The Certification Authority Authorization record specifies which certificate authorities (CAs) are permitted to issue SSL/TLS certificates for a domain.

  • Example: example.com. 3600 IN CAA 0 issue "letsencrypt.org"
  • Use: CAA records prevent unauthorized certificate issuance. CAs are required (per RFC 8659) to check CAA records before issuing a certificate. If no CAA record exists, any CA may issue. Adding CAA records is a low-effort security improvement.

Checking Your Records

Misconfigured DNS records are one of the most common causes of email delivery failures and website downtime. Use our DNS lookup tool to query any record type for any domain, and run a full domain analysis to check that your MX, SPF, DKIM, and DMARC records are all correctly configured.

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More glossary terms

DNS Ports Explained

Understand which network ports DNS uses, including port 53 for standard queries, port 443 for DNS over HTTPS, and port 853 for DNS over TLS.

How Do IP Addresses Work?

Understand how IP addresses work, including IPv4 vs IPv6 formats, public vs private addresses, static vs dynamic assignment, NAT, and CIDR notation.

SMTP Ports Explained: 25, 465, 587, and 2525

Understand the four SMTP ports, when to use each one, the difference between STARTTLS and implicit TLS, and why ISPs block port 25.

What Is DKIM (DomainKeys Identified Mail)?

Learn how DKIM uses cryptographic signatures to authenticate email, including selector records, public/private key pairs, and the verification process per RFC 6376.

What Is DMARC?

Understand DMARC, how it builds on SPF and DKIM with alignment checks, policy options (none, quarantine, reject), and aggregate vs forensic reporting per RFC 7489.

What Is DNS (Domain Name System)?

Learn how the Domain Name System works, including recursive and iterative queries, root servers, caching, and TTL values. A technical overview referencing RFC 1035.

What Is Secure DNS (DoH and DoT)?

Learn about secure DNS protocols including DNS over HTTPS, DNS over TLS, and DNSSEC. Understand why standard DNS is insecure and how to protect your queries.

What Is a Domain Name?

Learn what a domain name is, how domains map to IP addresses via DNS, the difference between TLD types, and how subdomains, URLs, and hostnames relate.

What Is a Gateway IP Address?

Learn what a gateway IP address is, how default gateways route traffic between networks, and how to find your gateway address on any operating system.

What Is a Reverse Lookup?

Understand reverse lookups including reverse DNS (PTR records), reverse IP lookups, and reverse email lookups. Learn how each works, common use cases, and limitations.

What Is a Reverse Proxy?

Learn how reverse proxies work, the difference between forward and reverse proxies, and common use cases including load balancing, SSL termination, and caching.

What Is an Email Bounce?

Understand email bounces, the difference between hard and soft bounces, common SMTP error codes, and how bounces affect sender reputation.

What Is an Email Domain Name?

Learn what an email domain is, how the @domain.com part of email addresses works with MX records to route messages, and the difference between free and custom email domains.

What Is an SMTP Server?

Learn how SMTP servers work, the difference between MTA, MSA, and MDA, and how email is delivered hop by hop using the SMTP protocol defined in RFC 5321.

What Is an SPF Record?

Understand SPF records, how they authorize email senders, the TXT record format, and how receivers evaluate SPF results including pass, fail, and softfail.

What Is an SSL Certificate?

Learn how SSL/TLS certificates encrypt internet traffic, how the chain of trust works, the difference between DV, OV, and EV certificates, and why TLS replaced SSL.