DNS (Domain Name System)
About 5 min read
Last updated: 2026-03-15
What Is DNS
DNS (Domain Name System) is a system that translates human-readable domain names (e.g., example.com) into IP addresses (e.g., 93.184.216.34) that computers use for communication. Often compared to the internet's "phone book," a DNS query takes place behind the scenes every time you enter a URL in your web browser.
Without DNS, you would need to type in an IP address directly every time you wanted to visit a website. DNS is a foundational technology that underpins the usability of the internet, and its failure can affect the entire internet.
The Name Resolution Process
When you access www.example.com in your browser, DNS name resolution proceeds in the following order.
- Browser cache: If a record from a previous visit exists in the browser, it is used.
- OS cache: If not found in the browser, the OS resolver cache is checked.
- Full resolver (caching DNS server): A query is sent to the ISP or a public DNS server (e.g.,
8.8.8.8). If a cached record exists, the response is returned here. - Root DNS server: If no cache exists, the root server is queried for the authority over
.com. - TLD server: The TLD server managing
.comis queried for the authoritative server forexample.com. - Authoritative DNS server: The authoritative server for
example.comreturns the final IP address.
This entire process typically completes in a few tens of milliseconds. When caching is effective, a response can be returned in under 1 millisecond.
Public DNS Options
Using a public DNS instead of your ISP's default DNS server can sometimes improve response speed and privacy.
To switch to a public DNS, change the DNS server address in your router's DHCP settings, or configure it individually in each device's network settings.
DNS Security Risks and Countermeasures
Traditional DNS communication is unencrypted, posing several serious risks.
- DNS spoofing (cache poisoning): An attack that injects forged DNS responses to redirect users to phishing sites. DNSSEC (DNS Security Extensions) can verify the authenticity of responses, but adoption remains low.
- DNS leak: A problem where DNS queries leak outside the VPN tunnel, revealing your browsing destinations to your ISP.
- Eavesdropping: Plaintext DNS queries can be intercepted by anyone on the network, exposing which sites you are visiting.
To counter these risks, encryption via DNS over HTTPS (DoH) or DNS over TLS (DoT) is recommended. Major browsers now offer DoH as a default or optional feature.
To learn more about this topic, see What Is a DNS Leak? Risks and Prevention When Using a VPN.
Common Misconceptions
- Changing your DNS makes the internet faster
- Changing DNS only improves name resolution response time. It does not affect download speeds or video buffering. However, if your ISP's DNS is slow, web pages may feel like they start loading faster.
- DNS is only used for web browsing
- DNS is used in all communications involving domain names, including email delivery (MX records), VPN connections, online gaming, and IoT device communication. If DNS goes down, virtually all communication except direct IP address access is affected.