MAC

macOS Sierra 10.12.0

sudo killall -HUP mDNSResponder

OSX 10.11.0

sudo killall -HUP mDNSResponder

OSX 10.10.4

sudo killall -HUP mDNSResponder

OSX 10.10.0 – 10.10.3

sudo discoveryutil mdnsflushcache

OSX 10.9  – 10.8 – 10.7

sudo killall -HUP mDNSResponder

OSX 10.5 – 10.6

sudo dscacheutil -flushcache

Windows

 

ipconfig /flushdns

Linux (depending on what you’re running)

 

/etc/init.d/named restart

/etc/init.d/nscd restart

Verification

To check if you have flushed the DNS cache:

On Linux or MAC:

tcpdump -A -s 0 udp port 53

Then open your browser, type a website name, and check if any traffic is related to the url.