What Is DNS? How the Domain Name System Works
DNS is the phone book of the internet: it turns names like ipchecks.app into the IP addresses computers actually use. This guide explains how it works, what the common record types mean, and how to check DNS for any domain.
DNS (Domain Name System) is the system that translates human-friendly domain names like ipchecks.app into the numeric IP address a computer needs to connect — for example 13.140.152.233. Without DNS you would have to memorize an IP address for every website. Every time you load a page, send an email or use an app, a DNS lookup happens in the background, usually in milliseconds.
What is DNS, really?
Every device on the internet is reached by an IP address. But people are bad at remembering strings of numbers, so we use domain names instead. DNS is the distributed database that links the two: it stores records that say "this domain points to that IP address (or mail server, or text value)".
It is called a system because no single server holds the answer. Instead, millions of DNS servers around the world work together in a hierarchy, and every one of them can answer a lookup for any public domain.
DNS does not just power websites. It is also used for email delivery (MX records), server verification (TXT records) and security checks such as blacklist checks of mail-server IPs.
How does a DNS lookup work?
When you type a domain into your browser, four steps happen in the background:
- Your device asks its recursive resolver — usually the DNS server your ISP or router configured. If the answer is cached, the lookup stops here.
- The resolver asks the root servers where to find the top-level domain (TLD) servers, for example the
.appor.comservers. - The TLD servers point to the authoritative server for the specific domain, the server that officially owns its records.
- The authoritative server returns the answer — the IP address (or another record) — which is passed back to your browser to open the connection.
The whole chain usually completes in under 50 milliseconds. Resolvers cache answers for the TTL (time to live) set on each record, which is why a DNS change can take a few hours to spread worldwide.
The most common DNS record types
| Record | What it does | Example |
|---|---|---|
| A | Maps a domain to an IPv4 address | ipchecks.app → 13.140.152.233 |
| AAAA | Maps a domain to an IPv6 address | ipchecks.app → 2001:db8::1 |
| MX | Tells other mail servers where to deliver email | mail.ipchecks.app (priority 10) |
| TXT | Free text, used for verification and SPF/DKIM | v=spf1 include:... ~all |
| CNAME | Aliases one domain to another | www → ipchecks.app |
| NS | Names the authoritative name servers for a domain | ns1.ipchecks.app |
| PTR | Maps an IP back to a name — used in reverse DNS | 233.152.140.13 → ipchecks.app |
You can look up any of these for a live domain in seconds with the DNS Lookup tool.
Which DNS server are you using?
Your device uses whatever recursive resolver your router or operating system is configured with. By default that is usually your ISP's DNS — which means your ISP can see every domain you visit. Many people switch to a public resolver such as Cloudflare (1.1.1.1), Google (8.8.8.8) or Quad9 (9.9.9.9) for more speed or better privacy.
Your DNS server choice matters for privacy: every lookup reveals which sites you visit, even the parts a browser hides. If you use a VPN, the VPN should handle your DNS too — otherwise the classic DNS leak happens: your traffic appears to come from the VPN, but your real DNS queries still go to your ISP. Run a DNS leak test to verify.
Why DNS matters for your privacy
A few things worth knowing about DNS and privacy:
- DNS is mostly unencrypted — traditional DNS (port 53) sends every query as plain text, readable by anyone on the network path. Modern alternatives like DNS over HTTPS (DoH) encrypt the queries.
- Your ISP sees your domains unless you use DoH or a different resolver. It cannot see the full URLs you visit, but it sees the domain names.
- DNS leaks defeat a VPN — if the VPN does not also route your DNS, part of your browsing history still leaks to your ISP.
- Fast DNS makes the web feel faster — a slow resolver adds latency to the very first request for every new domain.
Want to know what a website can learn about you overall? Read Can Websites See My IP?
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Run a DNS Lookup →Frequently asked questions
What is DNS?
DNS (Domain Name System) is the phone book of the internet. It translates human-friendly names like ipchecks.app into the numeric IP address (for example 13.140.152.233) that computers use to connect. Every time you open a website, a DNS lookup happens first to find the right server.
How does DNS work?
When you type a domain name, your device asks a recursive resolver, which checks its cache and then queries a chain of servers: the root servers, the TLD servers (like .com or .app), and finally the authoritative DNS server for that domain. That server returns the IP address, which is passed back to your browser.
What is an A record and an AAAA record?
An A record maps a domain name to an IPv4 address, like 13.140.152.233. An AAAA record maps a domain name to an IPv6 address, like 2001:db8::1. Most domains have both so they work over IPv4 and IPv6.
What is a DNS leak?
A DNS leak is when your device sends DNS queries to your ISP's servers instead of the encrypted DNS server your VPN configured. That means your browsing activity can be logged even while connected to a VPN. You can test for it with a DNS leak test.
What is the difference between DNS lookup and reverse DNS?
A DNS lookup (or forward lookup) translates a domain name into an IP address. A reverse DNS lookup does the opposite: it translates an IP address back into a domain name using a PTR record. Reverse DNS is often used for mail server authentication and logging.
How do I check the DNS records of a domain?
Use the IPChecks DNS Lookup tool: enter any domain and it shows A, AAAA, MX, TXT, NS and CNAME records. You can also do a reverse DNS lookup on any IP address to see what domain it points back to.