What is DNS?
Quick answer
DNS, the Domain Name System, is the internet’s address book. Computers find each other using numerical IP addresses, such as 93.184.215.14, but people prefer names like example.com. DNS translates domain names into IP addresses, so when you type a website’s name, your device can find the right server.
IP addresses and domain names
| IP address | Domain name | |
|---|---|---|
| Example | 142.250.80.46 | google.com |
| Used by | Computers and network equipment | People |
| Format | Numbers (IPv4) or numbers and letters (IPv6) | Words |
Every device on the internet uses an IP address; see what is my IP address. DNS is the system that connects the two.
How a DNS lookup works
- You type a web address into your browser; see what URL stands for.
- Your device asks a DNS resolver, usually run by your internet provider or a public service.
- If the resolver doesn’t already know the answer, it asks a root server.
- The root server points to the server for the top-level domain, such as .com.
- That server points to the domain’s own authoritative name server.
- The authoritative server returns the IP address.
- Your browser connects to that address and loads the page.
This usually happens in milliseconds, and answers are cached so repeat visits are even faster.
Common DNS record types
| Record | Purpose |
|---|---|
| A | Points a name to an IPv4 address |
| AAAA | Points a name to an IPv6 address |
| CNAME | Makes one name an alias of another |
| MX | Directs email to mail servers |
| TXT | Holds text, often used to verify domain ownership |
Who invented DNS?
American computer scientist Paul Mockapetris designed DNS in 1983. Before that, computers relied on a single text file listing every name and address, which became impossible to maintain as the internet grew.
The root servers
There are 13 named root server identities, labeled A to M, but each is run as many copies around the world, more than 1,000 in total.
When DNS goes wrong
DNS failures can make websites unreachable even though the sites are fine. Attackers sometimes try to redirect DNS to fake sites, which is one reason HTTPS matters; see what HTTPS adds to HTTP. To look up who registered a domain or IP, see Whois IP lookup.
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