Some Websites Are Not Loading? How to Diagnose and Fix DNS

Troubleshooting guide for DNS misconfigurations causing websites not to load. Learn common causes and step-by-step fixes for DNS issues on your system.

DNS Misconfiguration: Websites Not Loading

Last updated: July 2026

Most sites load fine, but a few consistently fail with “server not found” or DNS_PROBE_FINISHED_NXDOMAIN — while working on your phone’s mobile data. That pattern (some sites, some networks) is the signature of a DNS problem on your machine or router.

Step 1: Confirm it’s DNS

nslookup example.com
# or, more detail:
dig example.com

If this fails (SERVFAIL, NXDOMAIN, timeout) but nslookup example.com 8.8.8.8 succeeds, your configured resolver is the problem — Google’s public resolver answered fine. On Windows, run the same in PowerShell: nslookup example.com then nslookup example.com 8.8.8.8.

Step 2: Flush the DNS cache

A stale cached record keeps a fixed site broken for you long after it’s fixed for everyone else.

# Ubuntu (systemd-resolved)
sudo resolvectl flush-caches

# macOS
sudo dscacheutil -flushcache && sudo killall -HUP mDNSResponder
:: Windows (admin prompt)
ipconfig /flushdns

Browsers keep their own cache too — in Chrome, visit chrome://net-internals/#dns → Clear host cache.

Step 3: Switch to a public resolver

ISP resolvers are the most common culprit — slow, flaky, or quietly filtering. Set Cloudflare (1.1.1.1) or Google (8.8.8.8):

  • Ubuntu desktop: Settings → Network → gear icon → IPv4 → turn DNS Automatic off → enter 1.1.1.1, 8.8.8.8.
  • Ubuntu server (netplan): add under the interface: nameservers: {addresses: [1.1.1.1, 8.8.8.8]} then sudo netplan apply.
  • Windows: Settings → Network → adapter → DNS server assignment → Manual.
  • Better: set it on the router so every device benefits.

Retest the failing site immediately after.

Step 4: Check the hosts file

Malware, old dev entries, or “website blocker” tools leave overrides that beat DNS entirely:

cat /etc/hosts        # Linux/macOS
type C:\Windows\System32\drivers\etc\hosts   # Windows

Any line mapping the broken domain (e.g. 0.0.0.0 example.com) — delete it and save.

Still broken?

If dig resolves but the browser still fails, DNS is exonerated — you’re into HTTPS/firewall territory (try curl -I https://example.com to see the real error). If nothing resolves on your network but does elsewhere, reboot the router and check its DNS settings — consumer routers wedge their DNS forwarder more often than anyone admits. And if you run your own domain and other people can’t resolve your site, that’s a zone misconfiguration — verify your NS and A records with dig +trace yourdomain.com.

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