What Is an A Record? The Complete Guide to DNS Address Records

Q: Should I use A records or CNAME for subdomains?

- Use A records when you control the IP and it's stable - Use CNAME when pointing to a service (CDN, cloud hosting, SaaS) that manages their own IPs

2026-01-01 · Unified DNS Team · 8 min read

What Is an A Record?

An A record (Address record) is the most fundamental type of DNS record. It maps a domain name directly to an IPv4 address, telling browsers and other internet services where to find your website or application.

When someone types "google.com" into their browser, the DNS system looks up the A record for that domain to find the corresponding IP address (like 142.250.69.78), then connects to that server.

The Basics

A stands for "Address"
Maps domain names to IPv4 addresses (32-bit addresses like 142.250.69.78)
The IPv6 equivalent is called an AAAA record (quad-A record)
Every domain that hosts a website needs at least one A record

How A Records Work

When a user wants to visit your website, here's what happens:

User enters domain — They type "google.com" in their browser
DNS query initiated — The browser asks a DNS resolver "What's the IP for google.com?"
A record lookup — The resolver queries authoritative nameservers for the A record
IP returned — The A record returns the IPv4 address (e.g., 142.250.69.78)
Connection established — The browser connects to that IP address

A Record Structure

An A record consists of three main components:

Component	Example	Description
Name	@ or www	The hostname (@ represents the root domain)
TTL	3600	Time To Live in seconds (how long to cache)
Value	142.250.69.78	The IPv4 address

Example A Records

; Root domain pointing to web server
example.com.        3600    IN    A    104.21.32.150

; www subdomain pointing to same server
www.example.com.    3600    IN    A    104.21.32.150

; Mail server
mail.example.com.   3600    IN    A    172.67.182.31

; Application subdomain
app.example.com.    300     IN    A    52.84.125.99

A Record vs Other DNS Records

Understanding when to use an A record versus other record types is crucial:

A Record vs CNAME

A Record	CNAME
Points to an IP address	Points to another domain name
Can be used at the root domain (@)	Cannot be used at the root domain
Requires updating if IP changes	Automatically follows the target
Slightly faster resolution	Requires additional DNS lookup

When to use CNAME instead: When pointing to a service that might change IPs (like a CDN or cloud service), use a CNAME to their provided hostname.

A Record vs AAAA Record

A Record: Maps to IPv4 addresses (32-bit, e.g., 142.250.69.78)
AAAA Record: Maps to IPv6 addresses (128-bit, e.g., 2607:f8b0:4004:800::200e)

Modern best practice is to have both A and AAAA records for dual-stack compatibility.

Common Use Cases

1. Website Hosting

The most common use — pointing your domain to your web server:

example.com.      3600    IN    A    104.21.32.150
www.example.com.  3600    IN    A    104.21.32.150

2. Subdomains for Different Services

Create separate A records for different applications:

app.example.com.      300     IN    A    52.84.125.99
api.example.com.      300     IN    A    34.149.87.241
staging.example.com.  300     IN    A    35.192.45.123

3. Mail Server Configuration

Point mail subdomains to your mail server (used alongside MX records):

mail.example.com.     3600    IN    A    216.58.214.165

4. Load Balancing (Multiple A Records)

You can create multiple A records for the same hostname to distribute traffic:

example.com.    300    IN    A    142.250.69.78
example.com.    300    IN    A    142.250.69.79
example.com.    300    IN    A    142.250.69.80

DNS will rotate through these addresses (round-robin), providing basic load distribution.

Best Practices for MSPs

1. Document Everything

Maintain records of:

What each A record points to
Why it was created
Which client/project it belongs to
When it was last verified

2. Use Appropriate TTL Values

Scenario	Recommended TTL
Stable production sites	3600-86400 (1-24 hours)
Sites that might migrate	300-600 (5-10 minutes)
During migrations	60-300 (1-5 minutes)

Pro tip: Lower TTL before planned changes, then raise it after stabilization.

3. Implement Monitoring

Set up alerts for A record changes
Monitor for unauthorized modifications
Track DNS propagation after changes

4. Regular Audits

Verify A records point to active servers
Remove records for decommissioned services
Check for orphaned subdomains

5. Use DNS Management Tools

Managing A records across dozens of clients and multiple DNS providers is time-consuming. Tools like Unified DNS let you:

View all A records across all providers in one dashboard
Detect changes and unauthorized modifications
Maintain backups of all DNS configurations
Audit who changed what and when

Troubleshooting A Records

Record Not Resolving

Check propagation status:

# Using dig
dig google.com A

# Using nslookup
nslookup google.com

# Check specific nameserver
dig @8.8.8.8 google.com A

Common causes:

TTL hasn't expired (wait for propagation)
Typo in the record name or IP
Wrong DNS zone selected
Nameservers not properly delegated

Wrong IP Being Returned

Check if multiple A records exist
Verify you're editing the correct DNS zone
Check for CNAME conflicts (CNAME and A can't coexist for same name)
Clear local DNS cache: ipconfig /flushdns (Windows) or sudo dscacheutil -flushcache (Mac)

Intermittent Resolution

Multiple A records with one pointing to dead server
DNS provider issues
Network-level DNS interception

Frequently Asked Questions

Can I have multiple A records for the same domain?

Yes! Multiple A records for the same hostname create a round-robin rotation. DNS servers will return all IPs, and clients typically try the first one. This provides basic load distribution but isn't true load balancing.

What's the difference between A and AAAA records?

A records map to IPv4 addresses (32-bit), while AAAA records map to IPv6 addresses (128-bit). Most domains should have both for full internet compatibility.

How long does it take for A record changes to propagate?

Propagation depends on the TTL (Time To Live) setting. If TTL is 3600 seconds (1 hour), the change will fully propagate within that time. Some DNS resolvers may cache longer, so allow up to 48 hours for worldwide propagation in edge cases.

Can I use an A record for the root domain?

Yes, A records are the correct choice for root domains (@). Unlike CNAME records, A records can be used at the zone apex. Some providers offer "ALIAS" or "ANAME" records as alternatives that provide CNAME-like functionality at the root.

Should I use A records or CNAME for subdomains?

Use A records when you control the IP and it's stable
Use CNAME when pointing to a service (CDN, cloud hosting, SaaS) that manages their own IPs

What happens if my A record points to a non-existent IP?

The DNS resolution will succeed (the IP will be returned), but the connection will fail. Users will see timeout errors or "server not found" messages in their browser.

Get Started with Unified DNS

As an MSP managing dozens or hundreds of client domains, keeping track of A records across multiple DNS providers is challenging. Unified DNS lets you view, modify, audit, and backup all your DNS records from one dashboard — with automated syncing to Hudu and support for Cloudflare, Porkbun, NameSilo, and more.

Unified DNS is live — try it free for a month with code FREETRIAL2026 at billing setup. No commitment. Or request a demo for a walkthrough.