What is CNAME?

CNAME (Canonical Name) is a DNS record that makes one domain name an alias for another domain name.

In simpler terms: CNAME says: "this name is just another name for another domain".

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#Why CNAME is needed

CNAME is used to:

• point several names at the same resource
• avoid duplicating IP addresses in DNS
• simplify managing domains and subdomains

For example:

www.example.com -> example.com

www.example.com is not a separate site, just another name for example.com.

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#How CNAME works

1. The client requests:

www.example.com

2. DNS sees the CNAME:

www.example.com -> example.com

3. DNS then looks up records for example.com
4. It finds an A / AAAA record and returns the IP

A CNAME does not contain an IP address itself.

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#Example of a CNAME record

Simplified:

In total: www.example.com -> example.com -> 93.184.216.34

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#Important CNAME restrictions

This is often asked in interviews:

A CNAME cannot be used for the domain root (example.com) (in classic DNS)

A name with a CNAME must not have other DNS records (A and CNAME cannot coexist)

So:

• www.example.com -> CNAME is fine
• example.com -> usually A / AAAA

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#When CNAME is especially useful

• CDNs (Cloudflare, CloudFront, etc.)
• external services (GitHub Pages, Heroku)
• when the IP can change often
• when one service needs to be reachable under different names

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#Real-life example

CNAME is like:

• a person's alias
• there is one real name, but you can address them differently

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#Short interview answer

Remember this formulation:

CNAME is a DNS record that indicates one domain name is an alias for another domain name, and it redirects DNS resolution to it.