DNS Record Types Explained

Hi everyone,

Do you know that when ever we type any URL on bowser, what happens after that ?

Browser sends query to the DNS (Domain Name Server) server for that domain which is responsible for converting hostname into numerical IP address. As IP address is used to identify any device so it is important to fetch the value of it for particular domain. DNS server mainly responds with IP address of that domain or some time it responds with another domain name where we can query again to get IP address. But how browser will know that it received IP address or some other domain name. So, there is another parameter present in response which tells about the type of response that is called Record Types.

All Record Types fall into these categories —

1. A Record

2. AAAA Record

3. MX Record

4. TXT Record

5. CNAME Record

6. NS Record

Let’s understand each record type one by one —

A Record

A Record is the most fundamental record type and it indicates the IP address of the domain. For example - if you pull the IP address of youtube.com , you will get A record type with IP address as 172.217.24.78.

A record only holds IPv4 address. If any website has Ipv6 address , then record type of that website is AAAA record.

There is one more parameter called Time To Live (TTL) , which tells after how much time cached response will be deleted or refreshed. The default TTL for A record is 240 minutes, this means if an A record gets updated, it takes 240 minutes to get updated.

Some higher profile website have multiple A record. These website use technique called round robin load balancing to distribute the request traffic to one of the several IP address.

AAAA Record

DNS AAAA Record matches the domain name to IPv6 address. It is almost similar to the DNS A record. IPv6 is the latest version of Internet Protocol (IP). The main difference between IPv4 and IPv6 record is that IPv6 addresses are much longer than IPv4 addresses.

MX Record

DNS mail exchange records directs email to mail server. MX Record instruct mail server to route an email in accordance with Simple Mail Transfer Protocol (SMTP).

The components of MX record are domain name , record type , mail server , priority and TTL. The parameter priority represent which mail server is given how much priority. This number ranges from 0-65535, with 0 being the highest priority while 65535 is the lowest.

MTA (Message Transfer agent) software is responsible for querying MX records. When a user sends a email, MTA send DNS query to identify mail servers. MTA establish an SMTP connection with those mail servers based on the priority value.

TXT Record

TXT Record allows the domain administrator to enter text into DNS server. There is a specific format which is decided for storing attributes and values in TXT Record. The format is simply attribute and value contained within comma and separated by comma. One domain can have many TXT records.

The most important use case for TXT Record is email spam prevention and domain ownership verification. Email spam prevention mainly uses TXT records through SPF, DKIM, and DMARC. SPF tells receiving mail servers which servers are allowed to send email on behalf of your domain. DKIM ensures email content is not altered and confirms the sender’s domain. DMARC tells mail servers what to do if SPF or DKIM fails. TXT records are also used to prove you own a domain. Services gives you a unique token and browser add it into DNS TXT Record. Service queries DNS the token and if token matches then ownership is confirmed.

CNAME Record

A CNAME Record points to the domain or subdomain , never to IP address . Now DNS server will again send query to that domain or subdomain . This loop will continue until it gets IP address.

Those sites who have subdomains like blog.example.com or book.example.com , these subdomains will have CNAME Records that point to root domain. Suppose if IP address of host changes, only DNS A record for root domain needs to be changed and all the CNAME record will reflect same changes.

A CNAME record cannot coexist with any other record types like MX , TXT or A record for the exact same hostname. This is the limitation of standard DNS.

NS Record

NS stands for Name server. It tells which DNS server is authoritative for that domain. It is a type of DNS Server which stores all types of records for that domain like A , MX and CNAME record.

Almost all domains have multiple nameserver to increase the availability as there is one primary nameserver and several secondary nameserver which are copies of primary nameserver. Thus , if primary nameserver goes down , then DNS server can query to other secondary nameservers. Updating the primary nameserver will trigger an update of the secondary nameservers as well.

Conclusion

DNS record types are the backbone of how the internet works. Each record serves a specific purpose, and together they allow browsers, email servers, and other services to locate resources.

• NS records define which servers are authoritative for a domain, forming the foundation of DNS delegation.

• A and AAAA records map domain names to IPv4 and IPv6 addresses, making websites reachable.

• CNAME records provide flexibility by allowing one domain name to alias another.

• MX records control how email is routed and ensure messages reach the correct mail servers.

• TXT records enhance security by preventing email spoofing and enabling domain ownership verification.