Flushdns

Flushdns refers to clearing the DNS resolver cache on a computer or device. DNS caching stores recent hostname-to-IP mappings to speed up repeated lookups. Flushing the cache discards stored entries and forces the system to fetch fresh information from configured DNS servers.

Reasons to flush DNS cache include resolving websites that load an old or incorrect IP address, applying changes to DNS records after domain updates, troubleshooting connectivity issues, or addressing suspected DNS-related security concerns. Flushing can improve accuracy, but it may temporarily slow subsequent browsing as new lookups are performed and caches repopulate.

Platform-specific methods vary:

- Windows: open an elevated Command Prompt and run ipconfig /flushdns. A message confirming that the DNS Resolver Cache was successfully flushed indicates success.

- macOS: commands depend on the version. A common approach is sudo killall -HUP mDNSResponder. Some versions use sudo dscacheutil -flushcache, and others may require additional steps.

- Linux: methods depend on the DNS resolver in use. For systems with systemd-resolved, sudo systemd-resolve --flush-caches or sudo resolvectl flush-caches. For nscd, sudo service nscd restart or sudo /etc/init.d/nscd restart. For dnsmasq, sudo kill -HUP dnsmasq or sudo service dnsmasq restart.

- Android and iOS: there is no universal one-step flush. Common practices include toggling Airplane mode on and off, restarting the device, or clearing app-specific DNS settings where available.

Note that browser caches are separate from the OS DNS cache; flushing DNS cache affects system-wide hostname resolution, not necessarily the browser’s own cached data.