What Is DNS?
DNS (Domain Name System) is the internet's phone book. Every time you type a web address, DNS translates it into an IP address your device can connect to. A slow DNS server adds measurable delay to every single page load.
How DNS works — step by step
When you type speedtest.now into a browser, your device doesn't know the IP address of that server. DNS resolves this in milliseconds:
- Your device queries the DNS resolver — typically your ISP's DNS server by default, or a custom one you've configured (e.g. 8.8.8.8)
- The resolver checks its cache — if it has recently resolved
speedtest.now, it returns the cached IP immediately - Cache miss — recursive resolution — the resolver asks the root nameservers, which point to the
.nowTLD nameservers, which point to Speedtest.now's authoritative nameserver, which returns the IP - Your device receives the IP and connects to the server. This entire process takes 5–100 ms depending on DNS server location and load
The DNS lookup happens before any connection to the actual website. It adds to every page load for any domain not yet cached. On a slow DNS server, this adds 50–100 ms per new domain — perceptible when navigating between many different sites.
Why DNS affects browsing speed but not download speed
DNS only affects the time it takes to begin a connection, not the data transfer rate once connected. A faster DNS server makes pages appear to start loading faster — the initial connection is established more quickly. Once the connection is open, data transfer speed is determined entirely by your broadband bandwidth and the server's capacity. DNS has zero effect on throughput during an established connection.
This means: if your pages load slowly throughout the full page load (not just the first fraction of a second), the problem is bandwidth, not DNS.
DNS server comparison — speed
| Provider | Primary | Secondary | Avg latency | Privacy |
|---|---|---|---|---|
| Cloudflare | 1.1.1.1 | 1.0.0.1 | ~11 ms globally | Strong — no query logging |
| 8.8.8.8 | 8.8.4.4 | ~20 ms globally | Queries logged for analysis | |
| Quad9 | 9.9.9.9 | 149.112.112.112 | ~20 ms globally | Strong + malware blocking |
| OpenDNS | 208.67.222.222 | 208.67.220.220 | ~25 ms globally | Optional filtering available |
| Your ISP's default | Assigned via DHCP | — | Varies — often 30–80 ms | Queries logged by ISP |
DNS latency varies significantly by your location relative to the server. Cloudflare's 1.1.1.1 is generally the fastest globally due to their anycast infrastructure. Detailed DNS server comparison and how to change →
DNS over HTTPS (DoH) and DNS over TLS (DoT)
Traditional DNS queries travel in plain text — anyone on your network (your ISP, a Wi-Fi hotspot operator) can see every domain you look up. DNS over HTTPS (DoH) encrypts DNS queries inside HTTPS traffic, making them indistinguishable from regular web browsing.
DoH adds a small amount of overhead (1–5 ms per query) but eliminates DNS eavesdropping and prevents ISPs from monetising your browsing data via DNS logs. Most modern browsers support DoH directly in their settings. Cloudflare (1.1.1.1) and Google (8.8.8.8) both support DoH and DoT.
DNS caching — why most browsing is unaffected
DNS results are cached at multiple levels: your browser caches them, your operating system caches them, and your DNS resolver caches them. Each DNS record has a TTL (Time To Live) — typically 300 to 86400 seconds — after which the cache expires and a fresh lookup is needed.
In practice, most people visit the same domains repeatedly. After the first visit, subsequent visits to the same domain require no DNS lookup at all. DNS speed matters most when browsing many new domains — following links to unfamiliar sites, or loading pages that pull resources from dozens of third-party domains (analytics, fonts, ads).
How to test your DNS speed
Use the DNS Test tool to measure your current DNS resolver's response time. If you're seeing 60+ ms on DNS lookups, switching to Cloudflare 1.1.1.1 or Google 8.8.8.8 will noticeably improve the feel of web browsing — particularly on new domains.
How to change your DNS server
You can change DNS at three levels:
- Router level — change the DNS settings in your router's admin panel. All devices on the network use the new server automatically
- Operating system level — change in Network settings (Windows/macOS/Linux). Overrides router DNS for that device only
- Browser level — Chrome, Firefox, and Edge all support configuring DoH directly in browser settings. Only affects that browser