DNS, the domain name system, is the part of the internet that turns a human-friendly name like example.com into the numeric IP address a computer needs to open a connection. You type a name, your device asks a DNS server what address that name points to, and once it has the answer it connects to that address. Think of it as the internet phone book: you know the name, DNS finds the number. This explainer covers how a lookup actually resolves, the record types worth knowing, and why DNS is behind so many outages.
Why DNS exists
Computers route traffic using IP addresses, strings like 93.184.216.34 or longer IPv6 versions. People cannot remember those, and addresses change when a site moves servers. DNS adds a stable layer of names on top. You publish the name once; the address behind it can change freely, and visitors never notice. Without DNS you would have to know and update raw numbers for every site you visit, which is exactly the problem the system was built to remove.
How a DNS lookup works
- Check the cache — your device and your resolver first look for a recent answer they already saved.
- Ask the resolver — if there is no cached answer, a recursive resolver (often run by your ISP or a public service) takes over the search.
- Walk the hierarchy — the resolver asks a root server which server handles .com, asks that TLD server which server handles example.com, then asks that authoritative server for the actual record.
- Return and cache — the answer travels back, gets stored with a time-to-live, and your browser finally connects.
That whole chain usually finishes in tens of milliseconds because caching short-circuits most of it. The first visit does the full walk; later visits reuse the cached answer until its TTL expires.
Common DNS record types
| Record |
What it does |
Typical use |
| A |
Maps a name to an IPv4 address |
Point a domain at a server |
| AAAA |
Maps a name to an IPv6 address |
Same, for IPv6 |
| CNAME |
Aliases one name to another name |
Point www to the root domain |
| MX |
Names the mail servers for a domain |
Route email |
| TXT |
Stores arbitrary text |
Domain verification, email auth |
| NS |
Names the authoritative servers |
Delegate who answers for the zone |
You will touch A, CNAME, and MX records most. TTL is not a record type but a setting on each record that controls how long it can be cached. Lower it before a planned migration so changes take effect quickly.
Why DNS breaks (and why it gets blamed)
When a site looks down but the server is fine, DNS is a prime suspect. A typo in a record, a forgotten renewal, an expired TTL serving a stale address, or slow propagation after a change can all make a working site unreachable. Because DNS sits at the very start of every connection, a small mistake there looks like a total outage. The fix is usually to check the actual published record, not the server. DNS resolves the address; once connected, the request itself often travels over HTTP, the web request protocol.
What to skip
- Do not memorize every record type. Learn A, CNAME, MX, TXT, and TTL; look up the rest when a task needs them.
- Do not set huge TTLs before a migration. A long TTL means stale answers linger for hours after you change a record.
- Do not confuse DNS with hosting. DNS only points to where a site lives; it does not run the site.
- Do not ignore your resolver. A slow or filtered resolver can make browsing feel broken even when records are correct.
FAQ
What does DNS stand for?
Domain name system. It is the service that translates domain names people type into the IP addresses that computers use to connect.
Is DNS the same as an IP address?
No. An IP address is the actual numeric destination; DNS is the lookup system that finds the right IP address for a given name.
Why is DNS slow sometimes?
Usually the first lookup for a name has to walk the full hierarchy, while later ones are cached. A distant or overloaded resolver, or a misconfigured TTL, can also add delay.
Can changing DNS make my internet faster?
Switching to a faster public resolver can shave lookup time, but it does not change your connection speed once you are connected to a site.
Where to go next
See how a request travels after the lookup with HTTP, understand the content delivery network that often answers next, and lock down the network where lookups happen.