Why Change DNS at the Router Level
By default, your router hands out your ISP‘s DNS servers to every connected device via DHCP. Setting DNS on the router itself — rather than on each individual device — means every device on the network inherits the new resolver automatically, including devices you can‘t easily configure yourself (smart TVs, IoT sensors, guest devices).
Router-level DNS is the right layer for three common goals: faster page-load times from a lower-latency resolver, ad/tracker filtering through resolvers like NextDNS or AdGuard DNS, and defending against DNS hijacking, where malware or a compromised ISP silently redirects your DNS queries. If your router‘s DNS settings changed and you didn‘t do it, treat that as a compromise signal — check for unauthorized WAN DNS entries first.
Router DNS is a WAN-side setting, distinct from DNS cache, which is a local, per-device store of resolved lookups. If you‘re troubleshooting stale results after switching resolvers, see How to Flush DNS Cache — a router-level change won‘t clear cache already held by client devices.