A, AAAA, CNAME - Which DNS Record Do You Need?

When you create a subdomain you need to tell DNS where to send traffic. That's what DNS records do. Most of the time you'll only ever need three types.

A record - point to an IPv4 address

An A record maps your subdomain to a specific IPv4 address. If your server is at 203.0.113.42, you create an A record with that value. This is the most common record type and what you almost always want when you control the server.

Type:    A
Name:    myproject
Content: 203.0.113.42

AAAA record - point to an IPv6 address

Identical to an A record but for IPv6. If your host provides an IPv6 address alongside the IPv4 one, it's worth adding both - visitors with IPv6 connectivity will prefer it.

CNAME record - point to another hostname

A CNAME says "resolve this name like you would resolve that other name." It's perfect for services that don't give you a fixed IP - like GitHub Pages, Netlify, Render, or Railway - which give you a hostname to point at instead. You can't put a CNAME on a root domain, but subdomains are fine.

Type:    CNAME
Name:    myproject
Content: yourapp.onrender.com

Which one to use

Have an IP address? Use an A record. Given a hostname by your hosting provider? Use a CNAME. When in doubt, check your host's documentation - they'll tell you exactly what to create.