Every domain publishes a small, public instruction manual. It says where the website lives, which servers accept the domain’s email, and which outside services the owner has approved. That manual is its DNS records, and anyone can read it.
The records look cryptic at first: short type names, numbers with no labels, strings that end in dots. Once you know the handful of types that matter, though, you can read almost any domain’s setup in a minute. This guide explains each one with a realistic example, then walks you through a live lookup you can try yourself.
What DNS records are
DNS, the Domain Name System, is the internet’s address book. When you type a name like example.com, your device asks a DNS server what that name points to, and the answer comes from records the domain’s owner has published. Each record is one instruction of a particular type: “the website is at this address”, “email goes to this server”, “this company may send mail for us”. Records are public on purpose, because every computer on the internet needs to read them to reach the domain.
The records you’ll actually meet
The examples below use reserved documentation addresses, so they won’t match any real site, but they show the exact format you’ll see.
- A points a name to an IPv4 address. Example:
192.0.2.10. This is usually where the website is hosted. - AAAA does the same for an IPv6 address. Example:
2001:db8::10. If IPv6 is new to you, our guide to IPv4 vs IPv6 explains the difference. - CNAME makes one name an alias of another. Example:
www.example.comwith the valueexample.com. Whateverexample.compoints to,wwwfollows. - MX names a mail server and its priority. Example:
10 mail.example.com. The number is the priority: lower is tried first. - TXT holds free-form text for other systems to read. Example:
v=spf1 include:_spf.example.net -all. Mostly used for email security and ownership checks. - NS lists the name servers that hold the domain’s records. Example:
ns1.example.net. If you move DNS hosting, these change. - SOA, the start of authority, is housekeeping. Example:
ns1.example.net hostmaster.example.com 2026092601 7200 3600 1209600 3600. In order: the primary name server, the admin contact (the first dot stands for @), a serial number that goes up with each change, and timing values in seconds.
You may also see a trailing dot on names, like mail.example.com.. It just marks the name as complete and can be ignored.
Try it live
- Open our DNS lookup tool.
- Type
example.comand leave the type on A. Press Look up. You’ll get one or more IPv4 addresses: that’s where the site is served from. - Switch the type to MX. At the time of writing, example.com returns a single record:
0 .. That’s a “null MX”, a formal way of saying the domain accepts no email at all. - Switch to TXT. You’ll see
v=spf1 -allamong the results, which says no server is allowed to send email as example.com. Reserved example domains are set up this way so nobody can use them for spam.
The results table has three columns:
- Type is the record type. It’s usually the one you asked for, but an A lookup on an alias shows the CNAME first and then the address it leads to.
- Value is the record’s content, in the formats described above.
- TTL is how many seconds other servers may cache the answer. More on that below.
Now try a domain you use every day, such as your employer’s or your own. Checking the MX and TXT records of a domain you run is the fastest way to spot email setup problems. To see which address your own connection has, rather than a website’s, check your IP address on our homepage.
MX records and email
When someone sends an email to name@example.com, their mail server looks up the MX records for example.com to find out where to deliver it. Without them, mail has nowhere to go.
The priority number decides the order. A domain might publish 10 mx1.example.com and 20 mx2.example.com: senders try mx1 first and fall back to mx2 if it doesn’t answer. Records with the same number share the load.
If a domain has no MX records at all, many senders fall back to its A record and try to deliver there, which usually fails. A null MX like example.com’s 0 . removes the guesswork by stating plainly that the domain takes no mail. If your own domain should receive email and the DNS lookup shows no MX records, that’s the first thing to fix.
TXT records: verification and email security
TXT records are the domain’s notice board. Two uses cover almost everything you’ll find there.
Proving ownership. When you connect a domain to a service such as a search console, an email provider or a website builder, the service asks you to add a TXT record containing a unique code. It then looks up that code. Only someone who controls the domain’s DNS could have published it, so the service knows the domain is yours. These records often look like example-site-verification= followed by a long random string, and it’s normal for a busy domain to have a dozen of them.
Email security. Three standards work together to stop people from sending email that pretends to be from your domain:
- SPF lists the servers allowed to send mail for the domain. It lives in a TXT record on the domain itself and starts with
v=spf1. - DKIM publishes a public key that receiving servers use to check a signature on each email. It lives at a name like
selector._domainkey.example.com, where the selector is a label chosen by the domain’s email provider. - DMARC tells receivers what to do when a message fails those checks, such as reject it or send it to spam, and where to send reports. It lives at
_dmarc.example.com.
You can check all three with the DNS lookup tool: look up the domain’s TXT records for SPF, and _dmarc. plus the domain for DMARC.
TTL and why changes take time
DNS would be slow if every lookup went all the way to the domain’s name servers, so answers are cached. Your internet provider’s resolver, your router and your device all keep a copy for as long as the record’s TTL allows. A TTL of 3600 means one hour.
That’s why DNS changes don’t appear everywhere at once. If you move your site to a new server, anyone whose resolver cached the old address keeps getting it until that copy expires. People call this “propagation”, but nothing is actually spreading: old copies are simply running out.
It also explains why a friend might see different results than you. You’re asking different resolvers, and each cached the answer at a different moment. Some resolvers also keep answers a little longer than the TTL asks.
The practical tip: before a planned change, lower the TTL to something short, such as 300 seconds, a day in advance. After the change is done, raise it again.
Frequently asked questions
What is a DNS lookup?
A DNS lookup asks the Domain Name System for a domain’s records, such as the address its website uses or the servers that receive its email. Your device does this constantly in the background. A lookup tool lets you see the answers directly.
Is it legal to look up someone’s DNS records?
Yes. DNS is public by design: records are published so that any computer on the internet can find them. Looking them up is how the internet normally works.
What does NXDOMAIN mean?
NXDOMAIN means the name doesn’t exist in DNS. The domain may be mistyped, never registered or expired, or the subdomain was never created. It’s an answer from DNS, not an outage.
Why do I see different results than someone else?
You’re probably using different resolvers, and each caches answers for up to the record’s TTL. If a record changed recently, one of you may still be seeing the old copy. Large sites can also return different addresses depending on where you are, to send you to a nearby server.
What’s the difference between an A record and a CNAME record?
An A record points a name straight to an IPv4 address. A CNAME points a name to another name, which is then looked up in its place. Use a CNAME when you want a name to follow another one automatically, for example www following your main domain. A name that has a CNAME can’t have other records alongside it, which is why the bare domain usually uses A records instead.
How do I check a domain’s DNS records?
Enter the domain in a DNS lookup tool and choose the record type you want. To understand what the addresses you find actually are, our guide on what an IP address is is a good next read.