DNS Server Not Responding

What’s actually happening

Nothing resolves — browsers spin and then time out, and the Windows network troubleshooter reports the DNS server isn't responding (Windows 11 sometimes shortens this to "Can't reach DNS server"). Pinging an IP directly often still works, which proves the network is up and only name resolution is broken. It affects every app, not just the browser.

Common causes

• The configured resolver IP is wrong, offline, or belongs to a server that's been decommissioned.
• Router or local network outage — the box handing out DNS via DHCP is down or wedged.
• A firewall or security suite is blocking outbound UDP/TCP port 53.
• The ISP's resolver is having an outage.
• Stale DHCP lease left a bad DNS server address on the adapter.

How to fix it

1. Prove it's DNS and not the whole connectionping 1.1.1.1 (an IP, no DNS needed). If that succeeds but ping cloudflare.com fails, resolution is the only thing broken. nslookup example.com 8.8.8.8 tests a known-good server directly.
2. Switch to a public resolverSet the adapter's DNS to 1.1.1.1 / 8.8.8.8 (IPv4) or the matching IPv6 servers. On macOS: System Settings > Network > Details > DNS. On Windows: adapter properties > IPv4 > Use the following DNS server addresses. This resolves it whenever the original resolver was the problem.
3. Restart the router and renew the leasePower-cycle the router (30 seconds off). Then renew the client lease: Windows ipconfig /release && ipconfig /renew; macOS, click 'Renew DHCP Lease' in the network details.
4. Check the firewall / security softwareTemporarily disable third-party firewall/AV and retry. If lookups recover, add an allow rule for outbound port 53 (and 853 if you use DNS-over-TLS) rather than leaving it off.
5. Flush the cache after changing resolversWindows: ipconfig /flushdns. macOS: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder. Then retest in a fresh browser tab.