DNS errors are among the most common — and most misunderstood — problems on the internet. You might see messages like "DNS_PROBE_FINISHED_NX_DOMAIN," "Server DNS Address Could Not Be Found," or simply find that some websites load while others refuse to. This guide explains what DNS actually does in plain English, why it breaks, and gives you a complete set of fixes to try, from the simplest to the most technical.

What is DNS, in plain English?

The Domain Name System (DNS) is essentially the internet's phone book. When you type a web address like "bbc.co.uk" into your browser, your computer doesn't actually know how to find that server directly — it needs to look up the numerical IP address behind that name first (something like 151.101.0.81). DNS is the service that performs that lookup. When DNS breaks, your computer can no longer translate website names into the addresses it needs to connect to, even though your internet connection itself might be working perfectly well.

This is exactly why DNS errors are so confusing: you can often still use apps that connect directly to a known IP address, and your internet "works" in the sense that the connection is live, but websites simply won't resolve.

Common DNS error messages

  • "This site can't be reached — DNS_PROBE_FINISHED_NX_DOMAIN"
  • "DNS server not responding"
  • "Server DNS Address Could Not Be Found"
  • "Server IP address could not be found"
  • Pages that spin and time out without ever loading

Step 1: Confirm it's actually a DNS problem

  1. Try opening a website by typing a raw IP address directly into the browser (for example, 1.1.1.1 — Cloudflare's own DNS service page). If this loads but named websites don't, it strongly confirms a DNS issue.
  2. Try a couple of different well-known sites. If all of them fail to resolve but your internet connection is otherwise active (apps like Spotify or WhatsApp still work, for instance), DNS is very likely the cause.

Step 2: Flush your DNS cache

Windows keeps a local cache of recent DNS lookups to speed things up, but this cache can become corrupted or hold onto outdated, incorrect entries.

  1. Open Command Prompt as Administrator (right-click Start > Terminal (Admin), or search "cmd", right-click, Run as administrator).
  2. Run:
ipconfig /flushdns
  1. You should see the message "Successfully flushed the DNS Resolver Cache." Try loading a website again.

Pro tip: Also try flushing DNS at the browser level. In Chrome, visit chrome://net-internals/#dns and click Clear host cache. In Edge, the equivalent is edge://net-internals/#dns.

Step 3: Restart your DNS Client service

If flushing doesn't help, the underlying Windows DNS Client service itself may need restarting.

  1. Press Windows + R, type services.msc, and press Enter.
  2. Scroll down to DNS Client.
  3. Right-click it and select Restart.
  4. If it's not running at all, right-click and select Start.

Step 4: Change your DNS server to a public provider

Sometimes the DNS servers assigned automatically by your ISP are slow, overloaded, or temporarily malfunctioning. Switching to a reliable public DNS provider often fixes the problem instantly and can also improve everyday browsing speed.

Popular free public DNS providers:

  • Cloudflare: 1.1.1.1 and 1.0.0.1
  • Google: 8.8.8.8 and 8.8.4.4
  • Quad9: 9.9.9.9 (also blocks known malicious domains)

How to change DNS on Windows

  1. Right-click the network icon in the system tray and choose Open Network & Internet settings.
  2. Click your active connection (Wi-Fi or Ethernet), then Edit next to DNS server assignment.
  3. Change from Automatic (DHCP) to Manual.
  4. Toggle IPv4 on, and enter your preferred DNS server (e.g. 1.1.1.1) as the preferred DNS and a secondary one (e.g. 1.0.0.1) as alternate.
  5. Click Save, then run ipconfig /flushdns again in Command Prompt.

How to change DNS at the router level

Changing DNS on the router applies it to every device on your network, which is often more convenient than configuring each device individually.

  1. Log in to your router's admin page (commonly 192.168.1.1 or 192.168.0.1).
  2. Find the WAN Settings, Internet Settings, or DNS section (location varies by manufacturer).
  3. Switch from automatic/ISP-assigned DNS to manual, and enter your chosen public DNS addresses.
  4. Save and reboot the router.

Step 5: Reset the TCP/IP stack

A corrupted network stack can interfere with DNS resolution even when the DNS servers themselves are fine. In an elevated Command Prompt, run:

netsh winsock reset
netsh int ip reset
ipconfig /release
ipconfig /renew
ipconfig /flushdns

Restart your PC afterwards.

Step 6: Check your hosts file

The Windows hosts file allows manual overrides of DNS lookups, and can occasionally be modified by malware or a misconfigured application to block or redirect specific sites.

  1. Open Notepad as Administrator.
  2. Open the file at C:\Windows\System32\drivers\etc\hosts.
  3. Look for any suspicious entries below the commented-out example lines (lines starting with # are ignored and normal). Genuine entries pair an IP address with a domain name, like 127.0.0.1 somesite.com.
  4. If you see entries redirecting well-known sites (banks, search engines, antivirus vendor sites) to unfamiliar IP addresses, this is a red flag for malware — see our guide on removing viruses for next steps.
  5. Delete any suspicious lines, save the file, and flush DNS again.

Warning: Never delete the default lines in this file (the ones referring to localhost) unless you know exactly what they do — only remove lines you don't recognise or that look like malicious redirects.

Step 7: Disable DNS over HTTPS temporarily (for troubleshooting)

Modern browsers like Chrome and Firefox may use their own encrypted DNS settings (DNS over HTTPS) independent of your system settings, which can occasionally conflict with a corporate network, parental control filter, or VPN.

  • In Chrome: Settings > Privacy and security > Security, scroll to Use secure DNS and try toggling it off temporarily to test.
  • In Firefox: Settings > General > Network Settings, and look for Enable DNS over HTTPS.

If disabling this resolves the issue, you can either leave it off or select a specific, reliable provider from the dropdown instead of "Automatic."

Step 8: Check for malware or hijacked DNS settings

Some malware deliberately changes your DNS settings to redirect you to fake or ad-laden websites, or to intercept banking traffic. If DNS problems appeared suddenly, alongside unexpected pop-ups, browser redirects, or a changed homepage, run a full scan with Windows Defender or a reputable tool like Malwarebytes. See our articles on removing adware and browser hijackers and signs your computer is infected with malware for more detail.

Step 9: Test on another device or network

If a specific website never resolves on any device or network you try, the problem may be with that website's own DNS records rather than anything on your end — in this case, waiting or contacting the site is the only fix. You can check this using an online tool like a "DNS checker" from another connection (e.g. mobile data) to see if the domain resolves elsewhere.

Closing thoughts

DNS problems can look alarming because the error messages are technical and vague, but the underlying fixes are usually quick: flush the cache, switch to a reliable public DNS provider, and reset the network stack if needed. Keeping a public DNS provider like 1.1.1.1 or 8.8.8.8 configured on your router by default is a great habit that pre-empts many future DNS headaches, since it removes dependency on your ISP's own (sometimes unreliable) DNS infrastructure.

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