Guide
What is DNS? The domain name system explained
DNS, the Domain Name System, is the internet's phone book: it turns a domain name like yourbusiness.co.uk into the address of the server that holds your website. Your DNS records also tell the world where to deliver your email and prove that messages really come from you. Changes to DNS can take from minutes to a day or so to spread, which is why timing matters when you move a site.
How it works
What happens when someone visits your site
- Type the nameA visitor enters your domain
- Ask DNSTheir device asks for the server address
- Get the addressDNS replies with a number
- ConnectThe browser contacts that server
- Load the pageYour site appears
This all happens in a fraction of a second, and the answers are saved so repeat visits are quicker.
The basics
Why DNS exists
Computers find each other using numbers called IP addresses. People remember names. DNS connects the two, so you can type a name and your device finds the right number behind the scenes.
Your domain has a set of DNS records stored on name servers. When anyone asks about your domain, a name server answers from those records. You edit the records, usually in the control panel where your domain is managed, to change where your site, email and other services point.
The records
The DNS records you will actually use
| Record | What it does | Example use |
|---|---|---|
| A | Points a name to an IPv4 address | Send yourbusiness.co.uk to your web server |
| AAAA | Points a name to an IPv6 address | The same, for newer addresses |
| CNAME | Makes one name an alias for another | Point www to your main address |
| MX | Says where to deliver email | Send mail to your mail server |
| TXT | Holds text for verification and email security | SPF, DKIM and DMARC records |
| NS | Lists the name servers for the domain | Say which servers answer for you |
Worked example
Reading the DNS records of a small business domain
A typical small business domain has a handful of records. An A record points the main name to the web server. A second record or a CNAME points www to the same place. One or more MX records send email to the mail server.
There is also usually a TXT record for SPF, listing who may send mail for the domain, and another for DKIM, which signs outgoing messages. Some domains add a TXT record for DMARC, and others for verification by services such as search tools.
Together, this small set of records controls where your site loads from, where your mail is delivered and whether your messages are trusted. Knowing which record does what makes any change much less alarming.
Safety
Keeping DNS safe from mistakes and attackers
DNS has no undo button, so keep a copy of your records before you change anything. A screenshot or a text file is enough, and it lets you restore what worked if something goes wrong.
Protect the account where DNS is managed, because whoever controls it controls where your domain points. Use a strong, unique password and two-factor login, and keep the contact email current.
Quick reference
Which record to change for which job
| You want to | Change this |
|---|---|
| Move your website to a new host | The A record, or the name servers |
| Move your email to a new provider | The MX records |
| Make www go to the main site | A CNAME or an A record for www |
| Prove to others that mail is genuine | SPF, DKIM and DMARC TXT records |
| Verify the site with a search tool | A TXT record they give you |
Habits
Good DNS habits
Make one change at a time and test after each. Keep a dated copy of your records. Delete records you no longer need, because old entries can cause confusion and sometimes security problems. Finally, make sure more than one trusted person knows where DNS is managed, so a change is never blocked by someone who has left.
Ask for help
When to ask someone
If you are not sure what a record does, do not delete it. Ask the company that manages your domain or our live chat. Records you do not recognise are often needed by a service you forgot you use, such as email or a website verification, and removing them can break things that are hard to trace.
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Timing
TTL and why changes take time to spread
Each record has a time-to-live, or TTL, measured in seconds. It tells other servers how long they may keep an answer before asking again. A TTL of 3600 means an hour. Because many servers around the world keep copies, a change does not appear everywhere at once.
This is often called propagation. It is not a single process, just many caches expiring at different times. If you are about to move a website or email, lower the TTL a day or two beforehand, make the change, and raise it again afterwards. The switch will then spread much faster.
While the change spreads, some visitors see the old site and some the new one. That is why you keep the old hosting running until you are sure.
DNS and your email
MX records
These tell the world which server receives your mail. Wrong MX records mean email goes missing.
SPF
A TXT record listing the servers allowed to send mail for your domain.
DKIM and DMARC
Records that sign your mail and say what to do with messages that fail checks. See our email authentication guide.
Troubleshooting
Common DNS problems and fixes
If your website does not load after a change, check three things: that the A record points to the right address, that the name servers are the ones you intend, and that enough time has passed. If email stops, check the MX records first.
Use an online DNS lookup tool to see what the world sees for your domain. If it shows the old values, the change has not spread or was saved in the wrong place. A common cause is editing records in one control panel while the domain actually uses name servers elsewhere, so the changes never take effect.
- Site loads the old version: wait, and clear your browser cache
- Site shows a certificate warning: the domain may point to the wrong server for now
- Email bounces: check the MX records and the mailbox exists
- Only www works: add a CNAME or A record for the other version
- Changes have no effect: confirm which name servers the domain really uses
Where to edit
Name servers or individual records?
Change the name servers when
- You want your hosting company to manage all DNS
- You are moving a whole site and email to a new host
- You prefer one place for every record
Change individual records when
- You use several services for one domain
- Email is with one company and the website with another
- You only need to point one name somewhere
FAQ
Common questions
What is the difference between a domain and DNS?
A domain is your name. DNS is the system that links the name to servers for your website and email.
How long do DNS changes take?
From a few minutes to about a day, depending on the TTL and how widely the old answer was cached.
Can I edit DNS myself?
Yes. You edit records in the control panel where your name servers are managed.
Is DNS secure?
Basic DNS is open by design. Keep your domain account secure with a strong password and two-factor login.
What is a name server?
A server that holds your domain's DNS records and answers questions about it.
Keep reading
Related pages
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