An A record is a DNS record that maps a domain or subdomain name to an IPv4 address. It lets a browser find the server for a website or application using a readable name instead of a numeric address. A records work only with IPv4, while IPv6 destinations require AAAA records.
A record
What Is an A Record in DNS?
An A record, or Address record, maps a domain or subdomain to an IPv4 address. It lets browsers find a website or server by name instead of a numeric address. DNS is the wider naming system, and an A record is one record type within it.
How a DNS A Record Works
For example, app.example.com can point to 192.0.2.25, a documentation-only IPv4 address.
- A visitor enters app.example.com in a browser.
- The browser asks a DNS resolver for the address.
- The resolver finds the authoritative A record.
- It caches the answer for the record's TTL, or Time to Live.
- The browser connects to the IPv4 address.
A Record Fields and Example
Providers may display these fields differently.
| Field | Example | Meaning |
|---|---|---|
| Name | app | The hostname. @ commonly means the root domain. |
| Type | A | An IPv4 address record. |
| Value | 192.0.2.25 | The destination IPv4 address. |
| TTL | 300 | How long resolvers may cache the answer. |
www is a separate hostname and may need its own record or alias.
A Record vs. AAAA, CNAME, and MX Records
Each record type has a different purpose.
| Record | Target | Common use |
|---|---|---|
| A | IPv4 address | Website or app routing |
| AAAA | IPv6 address | IPv6 routing |
| CNAME | Another hostname | Hostname alias |
| MX | Mail server hostname | Email delivery |
Common Uses of A Records
An A record identifies a network destination. It does not configure HTTPS, hosting, or email.
- Pointing a root-domain website to a server.
- Routing subdomains such as app or api.
- Reaching self-hosted services by domain name.
- Connecting to IPv4 infrastructure.
Benefits of A Records
A records are simple and widely supported.
- They make IPv4 services available through memorable names.
- They route directly to an IP address.
- They can return multiple IPv4 addresses.
- They work with common hosting and DNS platforms.
Practical Limits and Risks
Plan DNS changes because cached answers do not update instantly.
- A records support IPv4 only. IPv6 requires an AAAA record.
- A TTL affects cache expiry, often mistaken for DNS propagation.
- A wrong address can cause an outage or send traffic to the wrong server.
- Multiple A records do not guarantee load balancing or high availability.
How to Change an A Record Safely
Use a deliberate process, especially during a migration.
- Confirm which provider is authoritative for the domain's DNS.
- Record the existing hostname, value, and TTL.
- Lower the TTL before a planned change when appropriate.
- Update the hostname with the new IPv4 address.
- Verify the answer with DNS lookup tools.
- Test HTTPS and application routing at the domain.
- Restore a sensible TTL after the change is stable.
DNS propagation means authoritative servers have new data. Resolver cache expiry determines when visitors receive it.
A Records When Publishing an Emergent App
Teams may use an A record to connect a custom domain to IPv4-based hosting or routing. When building with an AI app builder or an AI web app builder, include DNS, deployment, and HTTPS verification in the release checklist. Explore related terms in the Emergent glossary.
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