Glossary Term

A Record

glossary a record featured

An A record is a DNS record that maps a domain name to an IPv4 address. The “A” stands for Address, and the record is the step that turns a name like example.com into a number like 203.0.113.10 that a browser can connect to. Every website reachable over IPv4 depends on at least one A record, either directly or at the end of an alias chain.

How an A Record Works

An A record answers one question: which IPv4 address belongs to this name. It is defined in RFC 1035 (1987) as record type 1, and its value is always a single 32-bit address.

example.com.    3600    IN    A    203.0.113.10

Left to right: the hostname, a TTL of 3600 seconds, the internet class, the record type, and the IPv4 address.

The lookup runs in four steps:

  1. A visitor types example.com. The device asks a recursive resolver, usually run by the ISP or a public service such as Google Public DNS (8.8.8.8).
  2. The resolver walks down from the root servers to the .com servers to the domain’s authoritative nameserver.
  3. The authoritative nameserver returns the A record: 203.0.113.10.
  4. The resolver caches the answer for the TTL and hands it to the browser, which opens a connection to that IP.

An A record holds only an address. It never includes a port, a path, or a protocol, so 203.0.113.10:8080 or https:// cannot go in the value field.

A Record vs AAAA Record

An A record stores an IPv4 address. An AAAA record stores an IPv6 address. Otherwise they behave identically.

Aspect A record AAAA record
Address type IPv4, 32-bit IPv6, 128-bit
Example value 203.0.113.10 2001:db8::10
Defined in RFC 1035 (1987) RFC 3596 (2003)
Record type number 1 28

A domain can publish both at the same name. Dual-stack clients prefer IPv6 when it works and fall back to IPv4. If your server has no IPv6 address, publish only the A record. An AAAA record pointing at a dead address causes slow or failed loads for IPv6 users.

The other common comparison is with an alias record. An A record points a name to an IP, while a CNAME record points a name to another hostname and cannot sit at the root domain.

Common Types of A Record Setups

  • Single A record. One name, one IP. The standard setup for a site on one server.
  • Multiple A records (round robin DNS). Several A records at the same name, each with a different IP. Resolvers return all of them, usually in rotating order, which spreads traffic across servers. Round robin does no health checks, so a dead server still receives its share of visitors.
  • Wildcard A record. *.example.com answers for any subdomain that has no record of its own. Useful for multi-tenant apps, risky if forgotten.
  • Apex A record. An A record at the bare root domain (example.com). The apex cannot hold a CNAME, so an A record (or a provider’s ALIAS record) is how the root domain reaches a server.
  • Proxied A record. On Cloudflare with the proxy enabled, public lookups return Cloudflare edge IPs instead of your origin IP.

How to Add and Check an A Record

  1. Open the DNS editor at the provider that runs your nameservers. That is often not the registrar.
  2. Create a record of type A.
  3. Enter the host: @ for the root domain, or a label such as shop for shop.example.com.
  4. Enter the IPv4 address supplied by your host.
  5. Set the TTL. Use 300 seconds during setup or before a migration, then raise it to 3600.
  6. Save, then verify from the command line.
dig A example.com +short
nslookup -type=A example.com

A correct record returns the IP you entered. Changes reach new visitors within minutes. Resolvers holding the old answer keep it until the old TTL expires, which is why “DNS propagation” can appear to take up to 48 hours.

Branded short links are the exception to all of this. A subdomain such as go.yourbrand.com points to a link platform through a CNAME rather than an A record, because the platform manages its own server IPs.

Common A Record Mistakes

  • Stale IP after a server move. The old A record keeps sending visitors to a server that no longer hosts the site. Lower the TTL to 300 a day before migrating.
  • Conflicting records. An A record and a CNAME at the same name break resolution. Delete one.
  • Editing the wrong DNS zone. Changes made at the registrar do nothing if the nameservers point to Cloudflare or another host.
  • Expecting a redirect. An A record never changes the URL in the browser. Use a 301 redirect on the web server for that.
  • Leftover records. A records pointing at released cloud IPs can be claimed by someone else, a known cause of subdomain takeover.

Frequently Asked Questions

What is an A record in DNS?

An A record is the DNS record that links a domain or subdomain to an IPv4 address. When someone visits the domain, resolvers read the A record to find the server to connect to. It is the most basic and most common DNS record type. Without it, or an alias leading to one, an IPv4 visitor cannot reach the site.

What does the A in A record stand for?

The A stands for Address. RFC 1035 named it as the host address record when DNS was standardized in 1987. Its IPv6 counterpart was named AAAA because an IPv6 address is four times as long as an IPv4 address.

Can a domain have multiple A records?

Yes, a single name can have several A records with different IP addresses. Resolvers return the full set, and clients usually try them in the order received. This round robin setup distributes load across servers. It does not detect outages, so pair it with monitoring or use a load balancer for failover.

How long does an A record change take?

A new A record usually resolves within minutes. An edited record takes up to the previous TTL to reach everyone, because resolvers serve the cached old IP until it expires. With a 3600 second TTL, the worst case is about an hour. Lowering the TTL before the change shortens that window.

Is an A record the same as a DNS record?

No, an A record is one type of DNS record. Others include AAAA (IPv6 address), CNAME (alias), MX (mail server), TXT (verification and email policy), and NS (nameservers). The A record is the type that directly maps a name to an IPv4 address.

To put a branded subdomain on your short links without touching your site’s A records, connect it with linkutm branded domains.

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