What Is an A Record in DNS?

The “A” in A record stands for address. This type of record (sometimes called a host record) holds the IPv4 IP address for any given domain. When a user visits a website, their browser looks up the matching A record through the DNS: it sends a query for the domain name, and the answer that comes back is the IPv4 address of the server to connect to.

Anatomy of an A record

In standard zone-file notation, a complete A record looks like this:

example.com. 3600 IN A 192.0.2.44

Reading left to right: example.com. is the hostname the record answers for — in most DNS panels you enter @ for the root domain or a prefix such as www or blog for a subdomain. 3600 is the TTL (time to live) in seconds: how long resolvers may cache the answer before asking again — an hour, in this case. IN is the record class (Internet), A is the record type, and 192.0.2.44 is the IPv4 address the name resolves to (an address from the 192.0.2.0/24 block that RFC 5737 reserves for documentation examples). The A record type was defined in RFC 1035, the 1987 specification that still governs core DNS behavior.

A record vs. CNAME record

An A record points a hostname directly at an IPv4 address. A CNAME record instead aliases one hostname to another hostname, and resolvers continue the lookup with the new name until they reach an address record.

Use an A record at the root (apex) domain — DNS rules don’t allow a CNAME to coexist with the other records the apex needs, especially the required SOA and NS records — or whenever the server’s IP address is stable and under your control.

Use a CNAME record when pointing a subdomain such as www at a platform hostname whose underlying IP may change, so the platform can renumber its servers without you ever touching your DNS.

A record vs. AAAA record

An A record holds a 32-bit IPv4 address in dotted-quad form, such as 192.0.2.44. An AAAA record does the same job for a 128-bit IPv6 address, such as 2001:db8::1, and is defined separately in RFC 3596. A domain can carry both — and increasingly should, so that visitors on IPv6 networks connect natively while everyone else falls back to IPv4.

How to add or change an A record

Every DNS panel labels these fields a little differently, but the steps are the same:

1. Log in at the company that hosts your DNS, usually your registrar or web host, and open its DNS management area.
2. Add a new record and set its type to A.
3. Enter @ for the root domain, or a subdomain prefix such as www, in the host field.
4. Paste the server’s IPv4 address as the value.
5. Set the TTL and save. 3600 seconds (1 hour) is a sensible default for a stable server; drop it to 300 ahead of a planned move, then raise it back once the move is done.

Not sure which company hosts your DNS? Look up your domain’s nameservers, listed in your registrar account or in a whois lookup: the company running those nameservers is where you edit records. Our guide to nameservers vs. DNS explains how the two work together.

In the DreamHost panel, DNS records live on the Manage Websites page: open the site’s menu, click DNS Settings, then Add Record.

Keep in mind that an A record answers only for the exact hostname in its host field: a record for @ covers example.com but not www.example.com, so @, www, and any other subdomains each need their own record unless a wildcard (*) record or a provider aliasing feature covers them.

The change won’t reach every visitor at once. Resolvers keep serving the old address until their cached copy expires — a wait known as propagation, governed by the record’s TTL. Before a planned IP change, lower the TTL at least one full existing-TTL interval before you switch: resolvers that cached the record under the old TTL can keep serving the old answer for that entire period, so a record with an 86,400-second (24-hour) TTL needs its TTL lowered more than 24 hours ahead of the cutover. Keep the old server running until that old interval has fully elapsed.

How to check a domain’s A record

The quickest check is a terminal command: dig example.com A +short prints the IPv4 address (or addresses) the hostname currently resolves to. On Windows, nslookup example.com does the same job. Both normally answer from your network’s resolver cache, so to bypass it, ask a public resolver directly: dig @8.8.8.8 example.com A sends the query straight to Google’s resolver.

To see the answer from dozens of locations worldwide, use a web-based checker such as whatsmydns.net. After any change, look up both the bare domain and the www hostname to confirm each one resolves to the new address.