You type a name into a browser, and the page opens. Between those two events sits a conversation lasting milliseconds, one you almost never notice until it fails.
That conversation is DNS. Understanding it explains a lot of oddities routinely misdiagnosed as "slow internet".
The idea in one sentence
DNS translates names humans can remember into addresses machines use.
Devices on the internet reach each other using IP addresses — strings of numbers like
142.250.4.100. People can't remember those, so we use names. DNS is the layer
bridging the two.
The usual analogy is a phone book, and it's accurate enough as a starting picture. But one difference matters: a phone book is printed once, while DNS is answered again and again by machines spread across the world. That's why a site can move servers without a single visitor having to change anything.
The journey of one request
When you open a name you haven't visited before, the sequence goes like this:
The browser checks its own cache
If the name was opened recently, the answer is still stored and the journey ends here. This is why a second visit to the same site feels quicker to start.
The operating system checks its cache
Windows, macOS, Android, and iOS each store recent DNS results. Some systems also read a hosts file, whose contents override any answer from outside.
The request goes to a resolver
A resolver is the server tasked with finding the answer. By default, yours is supplied by your internet provider through automatic settings on the router.
The resolver works down from the root
If the resolver hasn't cached the answer, it asks in stages: the root servers, then the
servers handling suffixes like .com or .id, then the servers that
actually hold the records for that name.
The answer comes back and is cached
The IP address reaches your device, and every point along the way keeps a copy for a set period.
The whole sequence usually finishes in 20 to 120 milliseconds. For a name already cached, it's close to zero.
Why site changes don't appear immediately
That caching explains one of the most confusing complaints: a site has been moved to a new server, but some people still see the old page.
Every DNS record carries a number called TTL — how long the answer may be stored before it must be asked again. Common values run from five minutes to twenty-four hours.
Until the TTL expires, nothing can force the world to see the new address. All you can do is clear the cache on your own side:
- Windows — run
ipconfig /flushdnsin Command Prompt. - macOS —
sudo dscacheutil -flushcachein Terminal. - Android and iOS — turn on aeroplane mode for a few seconds, or restart the device.
- Browser — try a private window, which bypasses some caches.
Lower the TTL before moving servers, not after. If you plan to move a site, change the TTL to five minutes a few days ahead. Once every resolver is using that short value, the switch appears almost instantly. Lowering TTL after the move helps nothing.
Record types you'll come across
| Type | What it holds |
|---|---|
| A | The IPv4 address of a name |
| AAAA | The IPv6 address of a name |
| CNAME | A pointer saying one name follows another |
| MX | The servers that receive email for that domain |
| TXT | Free-form notes, often used to verify ownership |
| NS | Which servers are authoritative for that domain |
The MX record is worth remembering for one practical reason: email and the website can live with entirely different providers. Moving a site doesn't automatically move the email, and vice versa.
Symptoms rooted in DNS
Several complaints usually mistaken for a slow connection:
| Symptom | Likely cause |
|---|---|
| Pages slow to open, downloads fast | The resolver is slow to answer |
| Some sites won't open, the rest are fine | Bad DNS answers for particular names |
| Connected but "no internet" | The resolver isn't answering at all |
| Apps work, the browser doesn't | Some apps use their own DNS |
Confirming it is simple: open a site using its IP address directly. If that works while the name doesn't, the problem is DNS rather than your connection. The order of fixes is in the guide to a DNS server not responding.
When changing it makes sense
Your provider's default resolver is usually adequate. Changing it makes sense in three situations:
- The default resolver frequently fails to answer, which shows up as sites randomly failing to open.
- You want requests encrypted, so the names you look up aren't readable in transit.
- You want filtering at network level, for instance blocking certain categories across every device in the house at once.
The steps for phones, laptops, and routers are in the guide to changing DNS. The privacy side — including what your provider still sees even after you switch — is covered in the guide to public DNS and privacy.
What doesn't change afterwards
One thing worth setting straight, because expectations are often too high.
DNS only works at the very beginning, while a name is turned into an address. After that it plays no part at all. Changing DNS adds no download speed, doesn't fix stuttering video, and doesn't lower your ping while gaming.
What changes is the delay before a page starts loading — and only for names not already cached. If your complaint is speed, the cause lies elsewhere, and the order of checks is in the guide to fixing slow Wi-Fi.
Frequently asked questions
What does DNS do, simply put?
DNS translates site names that humans can remember into the IP addresses machines use. Without it you'd have to type strings of numbers to open every site, and sites couldn't move servers without changing the address everybody types.
Does changing DNS make the internet faster?
It adds no download speed at all. What shrinks is the delay before a page starts loading, and that's only noticeable if your provider's default DNS is genuinely slow to answer. The difference is usually tens of milliseconds per new name.
Why does a site that just moved servers still show the old page?
Because DNS answers are cached in several places at once — the browser, the operating system, the router, and your provider's resolver. Each keeps it for the TTL set by the domain owner, and the new page appears once that cache expires.
Can my ISP see which sites I visit through DNS?
If you use their default DNS and the requests aren't encrypted, yes — the list of site names you request is visible to them. The page contents stay protected by HTTPS, but the site name itself does not.
