DNS cache stores website IP addresses locally to speed up browsing. Sometimes it needs clearing when sites won't load or DNS changes.

Windows

Open Command Prompt (no admin needed) and run:

Command 
ipconfig /flushdns

Success message appears:

Command 
Successfully flushed the DNS Resolver Cache.

Done. DNS cache is cleared.

Mac

macOS Big Sur (11) and later:

Command 
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

macOS Catalina (10.15):

Command 
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

macOS Mojave (10.14) and earlier:

Command 
sudo killall -HUP mDNSResponder

Enter Mac password when prompted. No success message appears, but cache is flushed.

Linux

Ubuntu/Debian (systemd-resolved):

Command 
sudo systemd-resolve --flush-caches

Verify it worked:

Command 
sudo systemd-resolve --statistics

Look for "Current Cache Size: 0"

Using nscd:

Command 
sudo /etc/init.d/nscd restart

Using dnsmasq:

Command 
sudo /etc/init.d/dnsmasq restart

When to Flush DNS Cache

Websites won't load but internet works: DNS cache might have outdated or corrupt entries.

After changing DNS servers: Old cached results need clearing to use new DNS.

Domain recently changed IP: Cache still has old IP address.

Testing DNS changes: Verify updates propagated correctly.

Privacy/security: Clear browsing history at DNS level.

Browser DNS Cache

Browsers have separate DNS cache. Flush it too:

Chrome: Visit: chrome://net-internals/#dns Click "Clear host cache"

Firefox: Restart browser or visit about:networking#dns Click "Clear DNS Cache"

Edge: Visit: edge://net-internals/#dns Click "Clear host cache"

Verify DNS Flush Worked

Windows:

Command 
ipconfig /displaydns

Shows current DNS cache. Should be mostly empty after flush.

Test resolution:

Command 
nslookup google.com

Forces fresh DNS lookup.

Common Issues

"Access denied" on Windows: Open Command Prompt as Administrator (right-click > Run as administrator).

Mac command doesn't work: Check macOS version, use correct command for your version.

Linux - service not found: Your system might not use that DNS service. Try different command or check which DNS service is running.

Clear DNS and Reset Network

Windows - full network reset:

Command 
ipconfig /flushdns
ipconfig /release
ipconfig /renew

Flushes DNS, releases IP, gets new IP from router.

Mac:

Command 
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
networksetup -setairportpower en0 off
networksetup -setairportpower en0 on

Flushes DNS and restarts WiFi.

Bottom Line

Quick DNS flush commands:

Windows: ipconfig /flushdns Mac: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder Linux: sudo systemd-resolve --flush-caches

Also clear browser DNS cache for complete flush. Test with nslookup to verify.

Most common fix for "site won't load but internet works" problems.