A CNAME record makes one name an alias for another. Instead of giving www.example.com its own IP address, a CNAME can say it is the same as example.myshopify.com, and the address comes from there. The lookup above follows a name through every alias until it reaches a real address, names the service at the end of the chain, and warns you about dangling aliases that point to something that no longer exists.

What a CNAME Record Does

CNAME stands for canonical name. When a resolver looks up a name with a CNAME, it gets back a different name to look up instead, then repeats the lookup for that name until it finds an A or AAAA record with an actual IP address.

This is how most hosted services work. A store on Shopify, a site on GitHub Pages, Netlify or Vercel, a help center on Zendesk or a landing page on HubSpot all ask you to add a CNAME pointing to a name they control. When they move their servers, they update their own records, and your domain keeps working without any change on your side.

How to Read Your Result

The headline tells you whether the name is an alias and, if we recognize it, which service it belongs to. The Alias Chain shows every step in order: your name, each name it points to, and the final name with the addresses it resolves to.

When you enter a root domain such as example.com, the tool also checks www.example.com, because that is where the CNAME usually lives. A root domain normally has no CNAME of its own, so the result shows its addresses directly under Root Domain.

CNAME vs A Record

An A record points a name straight at an IP address. A CNAME points it at another name. Use an A record when you control the server and its address is stable. Use a CNAME when a service gives you a name to point to, because their addresses can change and the CNAME follows automatically.

A CNAME costs one extra lookup for each step in the chain, which adds a few milliseconds the first time a visitor loads the site. Most chains have one or two steps. Long chains, four or more, are worth shortening if you can.

Recognizing the Service Behind an Alias

The target of a CNAME usually gives away which service runs the site. Names ending in myshopify.com belong to Shopify, github.io to GitHub Pages, netlify.app to Netlify, cloudfront.net to Amazon CloudFront and azurewebsites.net to Microsoft Azure. The lookup recognizes more than 70 of these and labels each step in the chain, which is handy when you inherit a domain and need to work out where its subdomains are hosted, or when you’re auditing which services your organization still uses.

The Rules for CNAME Records

CNAMEs come with two rules from the DNS standards. A name with a CNAME can’t have any other records, so you can’t put a CNAME and an MX or TXT record on the same name. And because the root of a domain always needs NS and SOA records, the root can’t be a CNAME.

That’s a problem when a service asks you to point your root domain at a name rather than an address. Many DNS providers solve it with CNAME flattening or ALIAS records, which look up the target behind the scenes and answer with its addresses as if they were ordinary A records. If your root domain seems to behave like an alias, that is what’s happening, and it’s fine.

Mail servers have a rule of their own: MX records shouldn’t point to a CNAME. Point them at a name with its own A record instead.

Dangling CNAMEs and Subdomain Takeover

A dangling CNAME is an alias that points to a name that no longer exists. It usually happens when a company stops using a service, such as an old blog on a hosting platform, but forgets to delete the CNAME pointing to it.

This is more than untidy. On many platforms, anyone can create an account and claim an unused name. If an attacker claims the name your CNAME points to, your subdomain starts serving their content, on your domain, with your reputation. Security researchers call this a subdomain takeover, and it’s used for phishing pages and stealing cookies.

The fix is simple: delete CNAME records for services you no longer use, or point them somewhere you control. The lookup flags any alias that ends at a name that doesn’t exist, so it’s worth checking every subdomain your organization has used over the years.

How to Add a CNAME Record

In your DNS provider’s dashboard, add a new record, choose CNAME as the type, enter the host name you want to alias, such as www or shop, and paste the target the service gave you as the value. Most dashboards add your domain to the host automatically, so enter just www rather than www.example.com, or you may end up with www.example.com.example.com.

If the dashboard won’t let you save, there is probably another record on the same name, often an A record left over from an old setup. Remove it first, then add the CNAME. After saving, run the lookup to confirm the alias points where you expect and ends at a real address.

Common CNAME Problems

Most CNAME trouble comes from a short list of mistakes:

• A typo in the target, so the alias points to a name that doesn’t exist
• A leftover A record on the same name, which blocks the CNAME or causes conflicting answers
• The domain repeated in the host field, creating the alias on the wrong name
• An old CNAME for a service that was cancelled, which can lead to a takeover
• A CNAME on the root domain at a provider that doesn’t support flattening

Changes to CNAME records take up to the record’s TTL to reach everyone, so if the lookup still shows an old target, wait and check again. Nothing you look up here is saved or linked to you.