A Record

A DNS record that maps a domain name to an IPv4 address. The foundational building block of web hosting.

Oct 23, 2025 · About 1 min read

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An A record (Address Record) is a DNS record type that maps a domain name to an IPv4 address. When you type "example.com" into your browser, the DNS system uses the A record to find the server's IP address - essentially looking up the "street address" of the website.

Among the various DNS record types, the A record is the most fundamental and frequently used. It works alongside AAAA records (for IPv6 addresses) and CNAME records (which point to another domain name) as the core building blocks of DNS.

Setting up an A record is straightforward: you specify a domain name and an IP address, such as "example.com -> 93.184.216.34". You can create multiple A records for the same domain, enabling DNS round-robin load balancing across several servers.

When setting up a custom domain for a URL shortening service, understanding A records is essential. To point your domain (e.g., link.mycompany.com) to the shortening service, you configure either an A record or CNAME record in your DNS settings. A records point directly to an IP address, while CNAME records point to a domain name and automatically follow IP changes.

Every A record has a TTL (Time to Live) value that determines how long DNS resolvers cache the record. A TTL of 3600 means the record is cached for one hour. Shorter TTLs allow faster DNS propagation but increase query volume. Related books are available on Amazon.

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Related Terms

CNAME Record

A DNS record that maps one domain name to another, commonly used to point custom domains to URL shortening services.

DNS Resolution

The process of translating a human-readable domain name into the IP address of the server hosting the website.

Custom Domain

A privately owned domain name used with a URL shortening service instead of the service's default domain.

TTL

Time to Live - a value that specifies how long data should be cached or considered valid before being refreshed.

Server

A computer that provides data and services to other devices over a network. Web servers, mail servers, and DNS servers each handle different types of requests.

Wildcard DNS

A DNS configuration that uses an asterisk (*) to point all subdomains to a single IP address with one record, enabling efficient management of large numbers of subdomains.

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FAQ

When should I use an A record vs. a CNAME?

Use A records for root domains (example.com) since CNAME records cannot be set on root domains. For subdomains (www.example.com), CNAME is often more convenient as it automatically follows IP address changes.

How long does an A record change take to propagate?

It depends on the TTL setting. With a TTL of 3600 seconds (1 hour), old records may be cached for up to an hour. To speed up changes, lower the TTL to 300 seconds beforehand.

What happens if I set the wrong IP in an A record?

Your domain will point to the wrong server, making your site inaccessible or showing unintended content. Always note your current settings before making changes so you can quickly revert if needed.

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