What is DNS? It is the Domain Name System, the service that turns a name like yourbrand.com into the IP address of the server that holds your website. Computers connect using numbers, people remember names, and DNS sits in between.
This article is about the internet’s Domain Name System, not “DNS” as a medical or lab abbreviation. If you are here because something broke, jump to the troubleshooting table. If you run a website, read the middle sections first, because that is where most DNS damage happens: moving hosting, changing nameservers or adding an email service.
Two different DNS systems people mix up
Most beginner confusion comes from one fact. When people say “my DNS”, they can mean two completely separate things.
- The DNS resolver you use as a visitor. This is the server your phone or router asks when you open any website. By default it belongs to your internet provider. You can switch it to Google, Cloudflare or Quad9.
- The authoritative DNS for your domain. This is where the records for yourbrand.com are stored: where the website lives, where email goes, which services are verified. You manage it at your registrar, your host or a service like Cloudflare.
Changing the first affects only your own connection. Changing the second affects every visitor and every email sent to your domain. Both use the same name, which is why advice for one gets applied to the other.
What happens when someone opens your website
Here is the sequence, without the usual analogy:
- The browser checks its own cache. If it visited the site recently, it already has the IP address and skips the rest.
- If not, it asks the operating system, then the DNS resolver (your provider’s or the one you chose).
- The resolver asks a root server which servers handle .com.
- The .com servers reply with the nameservers for your domain.
- The resolver asks your nameservers for the address. They return the record, say 203.0.113.10.
- The browser connects to that address, and HTTPS starts from there. DNS finds the server, while the SSL certificate secures the connection to it. They are separate steps.
The resolver stores the answer for a set time, which is where TTL comes in later. You can watch this yourself:
dig yourdomain.com A +short
dig yourdomain.com NS +short
dig @8.8.8.8 yourdomain.com A +shortThe last line asks Google’s resolver directly. If it returns a different address from your provider’s resolver, you are looking at a stale cache, not a broken site.
DNS vs domain vs hosting
A domain is the name you rent from a registrar. Hosting is the server that stores your site. DNS is the set of instructions connecting the two, plus email and verification settings. You can buy a domain in one place, host in another and keep DNS in a third. That flexibility is useful, but it also explains why a site “goes down” when someone changes only one piece. If you are still setting up, our domain registration guide and web hosting guide cover the first two.
DNS records and what breaks when they are wrong
| Record | What it does | What breaks if it is wrong |
|---|---|---|
| A | Points a name to an IPv4 address | The website loads from the wrong server or not at all |
| AAAA | Same, for IPv6 | Some visitors get an old site while others get the new one |
| CNAME | Makes one name an alias of another | The subdomain stops resolving. A CNAME cannot sit alongside other records on the same name |
| MX | Says which servers receive email | Email bounces or lands on the old provider |
| TXT | Holds SPF, DKIM, DMARC and verification codes | Emails go to spam, and domain verification fails |
| NS | Lists the nameservers in charge of the domain | Every other record is ignored if it lives in the wrong place |
| CAA | Limits which authorities can issue certificates for the domain | SSL issuance is refused |
Email authentication records are covered in detail in our business email guide, including the rule that a domain can have only one SPF record.
Why “DNS propagation” is the wrong mental model
People say DNS changes “propagate” for 24 to 48 hours, as if the change is traveling around the world. It is not. Nothing is pushed anywhere. Resolvers cached your old answer, and each one keeps it until the TTL (time to live) runs out.
That changes how you should plan a move:
- Check the TTL on your current records. Many are 3600 seconds (one hour) or 14400 (four hours). Some defaults are longer.
- At least one full old TTL before the migration, lower it to something short, like 300 seconds. This must happen early, because resolvers already holding the old value will not look again until it expires.
- Make the change. Most visitors see the new server within minutes.
- After everything works, raise the TTL again so resolvers are not asking constantly.
Nameserver changes are slower because they are cached at the registry level, and for .com that can take up to about 48 hours. That is the case where the long wait is real.
To see how far a change has spread, query a few resolvers with dig @1.1.1.1 and dig @8.8.8.8, or use a public tool like whatsmydns.net.
The migration mistake that breaks email
This one deserves its own section because it is common and expensive.
There are two ways to point a domain at a new host. You can edit the A record, which moves only the website. Or you can change the nameservers to the new host’s, which moves control of all DNS to that host.
When you change nameservers, the new host’s DNS zone starts almost empty. Your MX, SPF, DKIM and verification records stay behind in the old zone, which is no longer being used. The website works, and then clients report that your emails are bouncing or not arriving.
Before any move:
- Export or screenshot every record in your current DNS zone. Look especially at MX and TXT.
- Recreate them in the new zone before you change the nameservers.
- Send a test email to and from your domain the same day.
- Keep the old hosting live for a few days until you are sure nothing still depends on it.
If you use Cloudflare, one more detail: the orange cloud (proxy) is for website records. Mail related records, including the hostname your MX points to, should be set to DNS only. Proxying them breaks mail delivery.
Check and change the DNS you use as a visitor
This is the part for the “my DNS” and “quad9 dns” searches.
Find which DNS you are using
- Windows: run
ipconfig /allin Command Prompt and look at “DNS Servers”. - macOS: run
scutil --dnsin Terminal. - Android: Settings, then Network, then Private DNS (the exact path varies by phone).
Common public resolvers
| Provider | Addresses | Android Private DNS hostname |
|---|---|---|
| Cloudflare | 1.1.1.1 and 1.0.0.1 | one.one.one.one |
| 8.8.8.8 and 8.8.4.4 | dns.google | |
| Quad9 | 9.9.9.9 and 149.112.112.112 | dns.quad9.net |
Quad9 blocks known malicious domains by default, which is why people choose it for security. Google Public DNS and Cloudflare focus on speed and reliability.
Set it on the router if you want every device in the house to use it, or on a single phone or laptop if you only need it there.
What changing it will and will not do. It can shorten the lookup before a page starts loading, mostly on first visits to a site. It does not raise your internet speed, lower your ping in games or improve video streaming quality once the connection is open. Those depend on your bandwidth and route. Switching DNS is useful when your provider’s resolver is slow or unreliable, and it is a quick test when one site will not load but others do.
DNS errors and quick fixes
| Error | Likely cause | What to try |
|---|---|---|
| DNS_PROBE_FINISHED_NXDOMAIN | The domain has no record, expired, or the resolver has a stale answer | Check the domain’s A record and expiry. Then flush the local cache |
| DNS server isn’t responding | The resolver is down or your connection is unstable | Restart the router, then switch to a public resolver |
| ERR_NAME_NOT_RESOLVED | The name does not resolve from your network | Test the domain on mobile data. If it works there, the issue is your network DNS |
| Site works for you but not for a client | Different resolvers hold different cached answers | Query the domain from other resolvers and wait out the TTL |
To flush the cache on Windows, run ipconfig /flushdns. On macOS, run sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder. On Android, turning airplane mode on and off clears most of it.
DNS, SEO and security
DNS is not a ranking factor, but its failures cost you rankings. If your nameservers are down, neither visitors nor Googlebot can reach the site. Repeated failures can lead to crawl problems and dropped pages. A slow DNS host also adds delay to the first request, so use a reliable provider for the zone rather than whatever came free with a cheap plan. This belongs on your monthly website maintenance checklist: confirm records, check expiry dates and make sure nobody edited the zone unexpectedly.
On the security side, lock your domain at the registrar and turn on two-step verification for that account. Someone who gets into your registrar or DNS login can redirect your website and intercept your email without touching your server. If your site has already been compromised, see our WordPress security guide. DNSSEC adds signatures to your DNS answers, and many registrars let you enable it with one setting, if your DNS host supports it.
What is DNS: FAQs
Q1. What is the purpose of DNS?
It lets people use readable names instead of IP addresses, and it also tells the internet where to send email for a domain.
Q2. What is a DNS server?
A server that answers DNS questions. Resolvers look up answers for users, and authoritative servers hold the official records for a domain.
Q3. How many DNS record types are there?
Dozens exist, but a normal business site uses a handful: A, AAAA, CNAME, MX, TXT, NS and sometimes CAA.
Q4. What is the difference between DNS and a domain?
The domain is the name. DNS is the system that maps that name to servers and services.
Q5. Is DNS the same as HTTPS?
No. DNS finds the server. HTTPS encrypts the connection to it.
Q6. Can DNS increase internet speed?
Not bandwidth. A faster resolver can reduce the lookup delay, which you notice mostly when opening sites for the first time.
Q7. How long do DNS changes take?
Record changes usually take minutes to a few hours, based on the TTL. Nameserver changes can take up to 48 hours.
Q8. Why does my site load for me but not for someone else?
Their resolver is probably holding an old answer. It will refresh when the TTL expires.
