supdns

A Records

The fundamental bridge between human-readable domain names and machine-readable IPv4 addresses.

What is an A Record?

An A record (Address record) is the most basic type of DNS record. It points a domain or subdomain to an IPv4 address. When you type "google.com" into your browser, an A record is what tells your computer that the website is located at 142.250.190.46.

Structure of an A Record

example.com. 3600 IN A 93.184.216.34
  • Host: The domain name (e.g., example.com or www).
  • TTL (Time to Live): How long (in seconds) the record should be cached by DNS resolvers.
  • Class: Usually IN (Internet).
  • Type: A.
  • Value: The 32-bit IPv4 address.

Primary Use Case

The primary use of an A record is to point your root domain (e.g., mysite.com) to the IP address of your web server. It is also used for subdomains like api.mysite.com.

Multiple A Records

You can have multiple A records for the same hostname. This is often used for Round Robin DNS load balancing, where the DNS server returns a different IP address each time to spread traffic across multiple servers.

A vs. CNAME

A common point of confusion is when to use an A record versus a CNAME record.

  • Use A Records when you have a static IP address.
  • Use CNAME Records when you want to point a subdomain to another domain name (e.g., pointing www to your root domain).
  • Important: You cannot have a CNAME at the root (apex) of a domain. You must use an A record (or an ALIAS record if your provider supports it) for your root domain.

Best Practice: TTL Management

If you are planning to move your website to a new server, lower your A record's TTL to 300 seconds (5 minutes) at least 24 hours before the move. This ensures that when you update the IP address, the change propagates quickly across the internet.