Guide
What is DNS?
Facts checked Oct 9, 2026
DNS (the Domain Name System) is the internet's phone book: it turns a name like yourshop.com into the number of the computer holding your website.
See who runs yours with Who hosts this website?
How it works
Computers find each other by numbers (IP addresses, like 192.0.2.10), which nobody can remember. DNS lets you use names instead.
- Someone types your address, or clicks a link to it.
- Their device asks a DNS lookup service, usually run by their internet or phone company, "What's the number for yourshop.com?"
- It asks your domain's name servers, the computers that hold your domain's entries, and passes the answer back.
- The browser goes to that number and opens your website. All of this takes a fraction of a second.
Email works the same way: a mail server looks up where to deliver mail for your domain. That's why a domain can point its website at one company and its email at another.
DNS records, in plain words
Each entry in your domain's part of the phone book is a DNS record. These are the ones you'll see:
| Record | In plain words | What it's for |
|---|---|---|
| A | "This name is at this number" | Points your domain at the computer holding your website |
| AAAA | The same, for the newer, longer kind of number (IPv6) | The same job as A; many sites have both, some only A |
| CNAME | "This name is another name for that one" | Often www, pointed at your website company's name for your site |
| MX | "Deliver mail for this domain here" | Your email. Delete these and your email stops. |
| TXT | A note other services can read | Proving the domain is yours, and the email settings that keep you out of spam (SPF, DKIM, DMARC) |
You'll also see NS records: they name your domain's name servers, the ones that hold all the others.
Setting them up for a new website, with the values to use: How to connect your domain to your website. For email: Get an email address with your domain name and Stop your emails going to spam.
Who controls your DNS?
Two jobs, often at one company but not always:
- Your registrar
- The company you rent the domain name from and pay each year. It tells the world which name servers hold your domain's records.
- Your DNS host
- The company that runs those name servers, so it holds your records. Often the registrar itself; sometimes your website builder, web host or a separate DNS service.
The catch: only the DNS host's records count. If your domain's name servers point at your website builder, records you change at the registrar do nothing. Find out which company runs your name servers first, and change records there.
How the domain, the website and email fit together: What's the difference between a domain, hosting and email?
Why DNS changes take time
Lookup services keep a copy of each answer for a while, so they don't ask every time. Each record says how long, in seconds: its TTL ("time to live"). 3600 means an hour.
- Change a record and some people get the old answer until their copy runs out, often within an hour, sometimes a day.
- Change name servers and it can take up to 48 hours.
- Meanwhile, some people see the old site and some the new. That's normal, and people call it "DNS propagation".
Tips for planning a change: Waiting for DNS.
When DNS goes wrong
- "This site can't be reached" or DNS_PROBE_FINISHED_NXDOMAIN: the phone book has no entry for that name. See "This site can't be reached".
- Website and email stopped together: often the domain has run out, which takes its DNS with it. See Domain name expired?
- Email stopped after a website change: the MX records were deleted or replaced. Ask whoever made the change to put them back.
How to see your DNS
- Run Who hosts this website? It names your registrar and the date the domain runs out, the company running your name servers (your DNS host), where your A and AAAA records lead (your web host) and where your MX records send email.
- For every record, and the TTLs, log in to your DNS host and open the domain's DNS settings (also called DNS records, DNS zone or Manage DNS).
- Write down who has the log-in. If nobody knows, that's the first thing to fix.
Send this to your web person
Not sure what to say? Copy this into an email, add your website's address, and send it.
Hi, Could you tell me about the DNS for our domain, [your domain]? 1. Which company is our registrar, and whose account is the domain in? 2. Which company runs our DNS (the name servers), and who has the log-in? 3. Could you send me a copy of our current DNS records, so we have them if anything changes? I'd like both accounts in [your organization]'s name, with my email address on them. Thanks