DNS & subdomains explained

If you're new to domains, this page explains the concepts you need to put a site online: what a subdomain is, how DNS works, and what each record type does — in plain language.

Domains vs subdomains

A domain like certed.one can have many subdomains in front of it. blog.certed.one and api.certed.one are both subdomains of certed.one. When you claim yourname.certed.one, you own that label and control where it points.

What is DNS?

DNS (the Domain Name System) is the internet's address book. When someone visits yourname.certed.one, their browser asks DNS "what server handles this name?" and DNS answers with the records you configured. Changes can take a few minutes to propagate across the network.

The record types you'll use

• A record — maps a name to an IPv4 address, e.g. 203.0.113.7. Use it when your host gives you a fixed IP.
• AAAA record — same as an A record but for IPv6 addresses.
• CNAME record — points your name at another hostname, e.g. username.github.io. Most managed hosts use this.
• TXT record — stores text, commonly used to verify ownership or configure email.

A record or CNAME — which do I use?

Rule of thumb: if your host gives you a domain name to point at, use a CNAME. If it gives you an IP address, use an A record. Managed platforms like GitHub Pages, Vercel and Netlify almost always want a CNAME.

Put it into practice

Ready to try it? Claim a free name in the quick start, then add your first record following managing DNS records. For host specifics see GitHub Pages or Vercel & Netlify.

Still have questions? Read the FAQ or create a free account to get started.