A Record
Address Record
The most fundamental DNS record: it maps a hostname directly to an IPv4 address, so that typing a domain name actually reaches a specific server. Almost every domain on the internet starts with at least one A record.
An A record (short for Address record) is the entry in a domain's DNS zone that answers the question every connection begins with: "what IPv4 address is this name?" When you enter example.com, your device asks a resolver for the domain's A record, receives an answer like 93.184.216.34, and only then can it open a TCP connection. Without an A record (or its IPv6 counterpart, the AAAA record), a name has no destination and nothing loads.
What an A record contains
An A record is deliberately simple — a name, a type, a time-to-live, and a single 32-bit IPv4 address:
; name TTL class type value
example.com. 3600 IN A 93.184.216.34
www.example.com. 3600 IN A 93.184.216.34
api.example.com. 300 IN A 203.0.113.10The TTL (3600 seconds above) tells resolvers how long they may cache the answer before asking again. The IN class means "Internet." The value is always a literal IPv4 address — an A record can never point at another name, which is the key distinction from a CNAME.
A record vs the other common record types
| Record | Maps | Returns |
|---|---|---|
| A | Hostname → IPv4 | A 32-bit IPv4 address directly |
| AAAA | Hostname → IPv6 | A 128-bit IPv6 address directly |
| CNAME | Hostname → hostname | Another name to resolve |
| MX | Domain → mail server | Priority + a hostname |
| TXT | Domain → text | Arbitrary text (SPF, verification) |
Multiple A records and round-robin DNS
A single hostname can carry several A records. When it does, the authoritative server returns all of them, and resolvers typically rotate the order they hand to clients. This is called round-robin DNS, and it gives a cheap form of load distribution and redundancy: if you list three web servers, roughly a third of visitors connect to each. The catch is that DNS has no awareness of whether a server is healthy or overloaded — it will keep handing out the IP of a server that crashed five minutes ago until you remove the record. For real resilience, round-robin is usually paired with a load balancer or a health-checking DNS service.
The root domain advantage
Unlike a CNAME, an A record is fully legal at the zone apex — the bare domain such as example.com with no subdomain. This is exactly why apex domains almost always use A records while subdomains like www or cdn often use CNAMEs. When a service only gives you a hostname (a CDN or load balancer) and you need it at the apex, providers offer workarounds such as CNAME flattening or ALIAS records that resolve the target server-side and return an A record to the client.
TTL, caching, and propagation
Every A record carries a TTL that controls how long resolvers cache it. A 3600-second TTL means an IP change can take up to an hour to be seen everywhere, because resolvers keep serving the cached value until it expires. The standard migration playbook is to lower the TTL (to 300 seconds or less) a day in advance, make the IP change, confirm it has spread, then raise the TTL back up to reduce query load. The lag between making a change and it being visible everywhere is what people mean by DNS propagation.
How to look up an A record
You can read any domain's A record from the command line:
# macOS / Linux
dig example.com A +short
# Windows
nslookup -type=A example.comThe reply is the IPv4 address (or addresses) currently published for that name — the same value your browser uses before it ever opens a connection.