A Record vs CNAME vs ALIAS: Which Should You Use?

When you're pointing a domain at a server or service, you're usually choosing between an A record, a CNAME, or an ALIAS (also called ANAME). They all accomplish the goal of making a domain resolve to something useful — but they work differently, have different limitations, and the wrong choice causes real problems.

A Record: The Foundation

An A record (Address record) maps a domain name directly to an IPv4 address:

yourdomain.com        A    203.0.113.10
www.yourdomain.com    A    203.0.113.10

When a resolver queries for yourdomain.com, it gets back 203.0.113.10 — a direct answer. Simple, fast, and works for any domain or subdomain.

Use an A record when:

• You know the IP address of your server and it's stable
• You're pointing your root domain (yourdomain.com) to your own server
• You need to point to a specific IP address

The limitation: If the IP address changes (you migrate servers, your hosting provider changes your IP), you have to update the A record manually. For services like AWS, Heroku, or Vercel that use dynamic hostnames (not fixed IPs), A records are impractical.

For IPv6 addresses, use an AAAA record — same concept, different address format.

CNAME: Pointing to Another Hostname

A CNAME record (Canonical Name) creates an alias — it maps one hostname to another hostname, not to an IP address:

www.yourdomain.com      CNAME    yourdomain.com
shop.yourdomain.com     CNAME    yourdomain.myshopify.com
app.yourdomain.com      CNAME    your-app.vercel.app

When a resolver queries www.yourdomain.com, it gets back a CNAME pointing to yourdomain.com, then resolves that to the actual IP. The client sees the final IP, but DNS made two hops.

Use a CNAME when:

• Pointing a subdomain to a third-party service (Vercel, Netlify, Heroku, Shopify, HubSpot)
• Pointing www to your apex domain
• The target hostname might change its IP — a CNAME stays correct automatically

The critical limitation — no CNAME at the root domain:

You cannot use a CNAME record on your root/apex domain (yourdomain.com itself, without www). This is a hard limitation in the DNS specification (RFC 1034).

The reason: a CNAME says "this name is an alias for another name — don't use any other records for this name." But your root domain needs to have SOA and NS records, which can't coexist with a CNAME.

This means you can't do:

yourdomain.com    CNAME    your-app.vercel.app    ← NOT VALID

This is why modern hosting providers give you both a hostname (for CNAME) and an IP (for A record). If you can't use a CNAME at the root, you use the IP address with an A record — accepting that you'll need to update it if the IP changes.

No CNAME chains: Pointing a CNAME to another CNAME (daisy-chaining) is technically valid but discouraged — it adds latency and creates fragile dependencies. Always point a CNAME to either an A record target or a final hostname.

ALIAS / ANAME: CNAME Behaviour at the Root Domain

The ALIAS record (called ANAME by some providers) was invented specifically to solve the "CNAME at root domain" problem. It's not part of the original DNS specification — it's a non-standard feature implemented by DNS providers.

yourdomain.com    ALIAS    your-app.vercel.app

From the outside, this looks like a regular A record — resolvers receive an IP address. Behind the scenes, your DNS provider resolves the target hostname and returns its current IP. If the target's IP changes, your DNS provider picks this up automatically.

Use an ALIAS when:

• You want to point your root domain to a service that gives you a hostname instead of a fixed IP (Vercel, Netlify, Heroku, AWS load balancers, etc.)
• Your DNS provider supports ALIAS/ANAME records

The limitation: Not all DNS providers support ALIAS/ANAME. It's a proprietary extension, so support varies:

Cloudflare is the special case: Cloudflare doesn't have a separate ALIAS record type. Instead, they automatically "flatten" CNAME records at the root domain — you add a CNAME at the root and Cloudflare resolves it to an IP and serves that IP to resolvers. It's ALIAS behaviour without needing a separate record type.

Practical Decision Guide

Pointing root domain to your own server with a fixed IP: → Use an A record

Pointing root domain to Vercel, Netlify, AWS ELB, or another service that gives you a hostname: → Use ALIAS/ANAME if your DNS provider supports it; or switch to Cloudflare and use a CNAME (Cloudflare flattens it automatically)

Pointing a subdomain (www, app, api, etc.) to a third-party service: → Use a CNAME

Pointing www to your root domain: → Use a CNAME: www CNAME yourdomain.com

Pointing www to the same place as your root, when root is an A record: → Use an A record for both pointing to the same IP, or a CNAME from www to yourdomain.com

What Happens When You Get It Wrong

CNAME on root domain: Your DNS provider may accept it, but behaviour is unpredictable. MX records stop working (because a CNAME says "use only the CNAME for this name"), meaning you lose inbound email. Many DNS providers now warn you or prevent this.

A record with a changing IP: Your site goes down when the IP changes until you update the record. Common when using cloud services that don't have fixed IPs.

CNAME chain: a CNAME b, b CNAME c, c A 1.2.3.4 — each hop adds latency. Some resolvers limit chain depth and may fail to resolve entirely.

Missing AAAA record when A record is present: Users on IPv6-only networks may not be able to reach your site. Add AAAA alongside A for full coverage.

Monitoring DNS Records

Regardless of which record type you use, DNS records can change unexpectedly — and when they do, your site or email breaks immediately.

Domain Monitor monitors your DNS records and alerts you the moment an unexpected change occurs. Whether it's a misconfigured deployment that overwrites your A record, an accidental deletion of a CNAME, or a DNS provider migration that missed a record — you'll know within minutes rather than hours.

Create a free account and add DNS monitoring for your domain. See DNS monitoring is here for Domain Monitor's DNS monitoring features.

For more detail on all DNS record types, see DNS record types explained and how to monitor MX, SPF, DKIM, and DMARC records.

Also in This Series

• What Happens When a Domain Expires? Full Lifecycle Explained
• Domain Grace Period vs Redemption Period vs Pending Delete
• Why Domain Auto-Renew Fails and How to Prevent It
• How to Monitor MX, SPF, DKIM, and DMARC Records
• What Is DNS Propagation and How Long Does It Take?