What Is DNS? A Records, MX Records and Nameservers Explained

You type "google.com" into your browser. A few hundred milliseconds later, Google's homepage appears. In that time, your computer has translated "google.com" into a specific IP address, something like 142.250.185.78, and connected to it. That translation is DNS.

DNS stands for Domain Name System. It is the phone book of the internet. Computers do not understand human-readable names. They work with numbers. DNS is the system that maps the names we type to the numbers they need.

Why DNS exists

Before DNS, the early internet used a single text file called HOSTS.TXT. It listed every computer on the network and its IP address. Every time a new computer was added, everyone had to download a new version. This worked when the internet was fifty machines. It stopped working when it was thousands.

DNS, designed in 1983 by Paul Mockapetris, solved that by making the naming system hierarchical and distributed. Instead of one giant file, authority is split across thousands of servers worldwide, each responsible for its own zone of the naming tree.

How a DNS lookup actually happens

When you visit a domain, your computer does not talk to just one DNS server. It asks a chain of them, in order:

The whole process takes 20 to 120 milliseconds the first time. Subsequent lookups for the same domain are instant, because everything is cached.

The main record types

DNS is not just about IP addresses. It stores many kinds of records, each answering a different question about the domain.

A record: the most common

Maps a domain to an IPv4 address. This is what most people mean when they say "DNS record." If you visit example.com and it works, there is an A record pointing example.com to an IP address.

example.com.    A    93.184.216.34

AAAA record: the IPv6 version

The IPv6 equivalent of an A record. Pronounced "quad-A." Maps a domain to an IPv6 address. Modern sites often have both A and AAAA records, so browsers with IPv6 connectivity use the IPv6 address and everyone else falls back to IPv4.

example.com.    AAAA    2606:2800:220:1:248:1893:25c8:1946

CNAME: alias to another name

Maps a domain to another domain, not to an IP. The resolver then looks up the target domain's A or AAAA record. Used for subdomains like www.example.com to example.com, or pointing a domain at a CDN.

www.example.com.    CNAME    example.com.
blog.example.com.   CNAME    myhost.cdnprovider.com.

One important rule: a CNAME cannot coexist with other records at the same name. You cannot have both a CNAME and an MX record on the same hostname. The DNS spec forbids it.

MX: mail exchanger

Tells the internet which servers handle email for the domain. MX records have a priority number. Lower numbers are tried first.

example.com.    MX    10    mail1.example.com.
example.com.    MX    20    mail2.example.com.

If your email is on Google Workspace, your MX records point to Google's mail servers (aspmx.l.google.com and similar). If you use Microsoft 365, they point to Microsoft's mail servers. This is the first thing to check when email for a domain stops working.

TXT: free-text records

Stores arbitrary text. Originally intended for human-readable notes, TXT records are now used for important verification and security data:

• SPF: lists the servers allowed to send email for your domain
• DKIM: contains a public key that email receivers use to verify messages are really from you
• DMARC: tells receivers what to do when email fails SPF or DKIM checks
• Domain ownership verification: services like Google Search Console, Meta, and Microsoft ask you to add a specific TXT record to prove you own the domain

NS: nameservers

Tells the internet which nameservers are authoritative for the domain, which is to say which servers actually hold the records. If you register a domain with one company and host the website with another, you point the NS records from the registrar to the hosting provider's nameservers.

example.com.    NS    ns1.registrar.com.
example.com.    NS    ns2.registrar.com.

Other record types

How to look up DNS records for any domain

Any DNS lookup tool lets you query any record type for any domain. This is useful for debugging (why is my email not arriving?), migration planning (what are the current records?) and security audits (does my domain have DNSSEC?).

1. Open the DNS Lookup tool.
2. Enter the domain: example.com.
3. Choose the record type: A, MX, TXT, NS, etc.
4. Read the results. The answer section shows the records, and the authority section shows the SOA/NS of the zone.

Common DNS problems and how to diagnose them

"My website is down"

Look up the A record for your domain. If it returns an IP, note it, then check whether the IP is the same one your hosting provider shows in their control panel. If it is different, the DNS is stale. You changed hosting but the record still points to the old server.

If the A record lookup returns NXDOMAIN, the domain is not registered or has expired. Check with your registrar.

"My email is not arriving"

Look up the MX records for your domain. They should point to the mail servers of whoever hosts your email (Google, Microsoft, Zoho, your hosting provider). If they are missing or point to the wrong place, email will not arrive.

Then look up TXT records. Check for an SPF record. It should list the servers allowed to send email for your domain. If SPF is missing or wrong, your outgoing mail will be marked as spam and rejected by many receiving servers.

"My DNS change has not propagated"

Look up the record from two different resolvers, Cloudflare (1.1.1.1) and Google (8.8.8.8). If they return different answers, one resolver is serving the old cached value. Wait for the TTL to expire, then re-check.

If you lowered the TTL before making the change, propagation takes minutes. If you changed the record without lowering the TTL, it can take up to 24 or 48 hours, depending on the TTL that was in place.

"Google Search Console cannot verify my domain"

The verification process asks you to add a specific TXT record. After adding it, look up the TXT records for your domain. If the record is not showing up, wait a few minutes and refresh. DNS is not instant. If it still does not show up after five minutes, the record was likely added incorrectly. Double-check the exact value, the hostname (usually @ or the root), and that you saved the change.

DNSSEC: a quick note

DNSSEC is a cryptographic extension to DNS that prevents certain kinds of attacks (DNS spoofing, cache poisoning). When it is set up correctly, resolvers return an "authenticated data" flag on their answers. Not all domains use it, but it is a good security practice.

If you look up a domain and see an "AD" badge on the result, that means the resolver validated the DNSSEC chain. If the badge is missing, the domain does not use DNSSEC, or validation failed.

The bottom line

DNS is invisible when it works and frustrating when it does not. Understanding the basic record types (A, AAAA, CNAME, MX, TXT, NS) is enough to diagnose almost every common problem: website down, email not arriving, verification failing, propagation delayed.

A DNS lookup tool is the diagnostic you reach for first. It costs nothing to look up any domain, any record type, from any browser. Bookmark it.