How a DNS lookup works
When you type example.com for the first time, the lookup goes through a chain of servers. It usually takes a few tens of milliseconds:
- Your device checks its own cache, then asks its configured resolver (your ISP's, or one you chose such as 1.1.1.1).
- If the resolver doesn't have the answer cached, it asks a root server, which points it to the servers for
.com. - The TLD server for .com points to the domain's authoritative name servers.
- The authoritative server returns the actual record, such as the IP address.
- The resolver returns the answer to your device and caches it for the time the record allows (its TTL).
In short: Most lookups are answered from a cache; the full chain runs only when the cached answer has expired.
Common DNS record types
| Record | What it holds |
|---|---|
| A | An IPv4 address for the name |
| AAAA | An IPv6 address for the name |
| CNAME | An alias pointing to another name |
| MX | The mail servers that receive email for the domain |
| TXT | Text used for verification and email security (SPF, DKIM, DMARC) |
| NS | The domain's authoritative name servers |
| PTR | Reverse DNS: the name for an IP address |
In short: Look any of these up with the DNS lookup tool.
Which DNS server am I using?
By default, your router hands out its own address or your ISP's resolvers, and devices use those. You can override this on the router (affecting every device) or on a single device. Browsers can also use encrypted DNS (DNS over HTTPS) independently of the system settings. Check the browser's privacy or security settings.
Public resolvers like Cloudflare 1.1.1.1, Google 8.8.8.8 and Quad9 9.9.9.9 are free. Switching can help if your ISP's resolver is slow, unreliable or filters domains you need. It doesn't bypass anything else your ISP does.
Does DNS affect internet speed?
DNS affects how quickly a website starts loading, not how fast data downloads. A slow resolver adds delay to the first connection to each new name; once connected, speed is the same. That's why changing DNS doesn't change your speed test result. Our website response time tool shows DNS time separately so you can see how much it contributes.
Fixing DNS problems
If some sites fail with “server not found” while others (or apps) work, DNS is a likely suspect:
- Restart the router, which clears its DNS cache and reconnects to the ISP's resolvers.
- Flush your device's cache (Windows:
ipconfig /flushdns) and restart the browser. - Try a public resolver (1.1.1.1 or 8.8.8.8) on the device. If sites load, your usual resolver is the problem.
- Turn off VPN or filtering apps that change DNS.
- For a site you manage, check its records with the DNS lookup and propagation checker.
Common questions
Will changing DNS make my internet faster?
It can make websites start loading slightly sooner if your current resolver is slow or unreliable, but it doesn't change download or upload speed. Your speed test result will be the same.
Which DNS server should I use?
Your ISP's resolver is used by default and is usually fine. Popular public alternatives are Cloudflare (1.1.1.1), Google (8.8.8.8) and Quad9 (9.9.9.9, which also blocks known malicious domains). Test a site you use often with each and keep what works reliably.
What does DNS_PROBE_FINISHED_NXDOMAIN mean?
The resolver says the name doesn't exist. Check the spelling; if the name is right, the domain may have expired or been misconfigured, or your resolver is failing. Try another DNS server to tell which.
What is DNS propagation?
After a DNS record changes, resolvers keep serving the old answer until their cached copy expires (the record's TTL). “Propagation” is simply caches expiring around the world, typically minutes to a day or two.