"Change your DNS to 8.8.8.8 and your speed will double." This advice is everywhere, and it is half right at best. Changing DNS can fix real problems, but it will not raise the download number in a speed test. Here is why.
What is DNS in the first place?
When you type a site name, your device does not know where that name lives. It asks a DNS server: "what is the IP address for this site?" The server replies with the address, and your device connects to it. Think of it as the internet's phone book.
That question happens once at the start and usually takes anywhere from a few to a few dozen milliseconds, after which the device remembers the answer for a while. From then on, all data flows directly between your device and the site with no involvement from the DNS server.
Why DNS does not raise your speed test result
Because a speed test measures how much data flows per second after the connection is made. DNS never touches that data. If you get 40 Mbps with your provider's DNS, you will get 40 with any other.
When changing DNS genuinely helps
1. When your provider's DNS is slow or unreliable
Some providers' DNS servers are slow to answer or occasionally fail. The symptoms are distinctive: a page "thinks" for a second or two before it starts loading, then loads at normal speed. Or you get a "server not found" message while other apps work fine.
2. When certain sites will not open at all
If particular sites never open while the internet otherwise works, your provider's DNS may be returning a wrong or stale answer. Switching to a public DNS can fix it instantly.
3. Privacy and protection
Some public DNS services block known malicious sites or content unsuitable for children, and some support encryption (DNS over HTTPS), so nobody on the network can see which sites you look up.
When it can make things worse
Content delivery networks (such as YouTube and Netflix servers located inside providers' own networks) sometimes rely on DNS to send you to the nearest server. If you use a distant DNS service, you may occasionally be sent to a further server and video gets slightly slower. Most large DNS services handle this well, but it is one reason your provider's own DNS can be the better choice when it works properly.
Well-known public DNS services
| Service | Primary | Secondary | Note |
|---|---|---|---|
| Cloudflare | 1.1.1.1 | 1.0.0.1 | Fast, privacy-focused |
| 8.8.8.8 | 8.8.4.4 | Widespread and stable | |
| Quad9 | 9.9.9.9 | 149.112.112.112 | Blocks known malicious domains |
| Cloudflare for Families | 1.1.1.3 | 1.0.0.3 | Blocks malware and adult content |
Where to change it
- On the router: applies to every device at home at once. Look for a DNS field in the WAN or DHCP settings. Note that some provider-supplied routers do not allow it.
- On Windows: Settings → Network & internet → connection properties → DNS server assignment → Manual.
- On Android: Settings → Network → Private DNS, then enter for example
one.one.one.oneordns.google. This works on both Wi-Fi and mobile data. - On iPhone: Wi-Fi settings → tap the network → Configure DNS → Manual. The change applies to that network only.
How to tell whether it helped
Do not rely on the speed test; it will not change. Instead, notice how long sites take to start appearing, especially ones you have not visited recently. The browser's developer tools (Network tab) show the "DNS lookup" time for each request if you want an exact figure.