Flush DNS in OS X

flushdns

#!/bin/bash
#
# flushdns
# This script will flush your DNS cache on Mac OS X 10.1 - 26.x
# The method for doing this chages it seems in every version of OS X,
# and I can never remember the correct command, so I wrote this script
# and gave it a name I could remeber.  
#
# v.2026-04-22 by bill@wellingtonnet.net
# https://gist.github.com/thewellington/6736175

OSX_VERSION=`sw_vers -productVersion`

echo "Attempting to flush DNS cache"

case $OSX_VERSION in
    # OS X 10.1 - 10.4 (Puma, Jaguar, Panther, and Tiger )
    10\.[1-4]*)
        echo "Flushing DNS cache for 10.1-10.4"
        
        lookupd -flushcache
        ;;
    # OS X 10.5 & 10.6 (Leopard and Snow Leopard)
    10\.[56]*)
        echo "Flushing DNS cache for OS X 10.5 - 10.6.*"

        dscacheutil -flushcache
        ;;
    # OS X 10.7 & 10.8 (Lion and Mountain Lion)
    10\.[78]*)
        echo "Flushing DNS cache for OS X 10.7 - 10.8.*"

        killall -HUP mDNSResponder
        ;;
    # OS X 10.9 (Mavericks)
    10\.9*)
        echo "Flushing DNS cache for OS X 10.9.*"

        dscacheutil -flushcache
        sudo killall -HUP mDNSResponder
        ;;
    # OS X 10.10 - 10.10.3 - the crappy times (Yosemite, part 1 )
    10\.10|10\.10\.[1-3])
        echo "Flushing DNS cache for OS X 10.10 - 10.10.3"

        sudo discoveryutil mdnsflushcache
        sudo discoveryutil udnsflushcache
        ;;
    # OS X 10.10.4 and up -- long live mDNSResponder! (Yosemite, part 2 )
    10\.10\.[4-5])
        echo "Flushing DNS cache for OS X 10.10.4+"

        dscacheutil -flushcache
        sudo killall -HUP mDNSResponder
        ;;
    # OS X 10.11 - 10.12.2 -- El Capitan, and Sierra
    10\.11|10\.12|10\.12.[1-2]*)
        echo "Flushing DNS cache for OS X 10.11 - 10.12.2"

        dscacheutil -flushcache
        sudo killall -HUP mDNSResponder
        ;;
    # macOS 10.12.3 - 10.15 -- Sierra, High Sierra, Mojave, and Catalina
    10\.12.[3-6]*|10\.1[3-5]*)
        echo "Flushing DNS cache for macOS 10.12.3 - 10.15.*"

        sudo killall -HUP mDNSResponder
        sudo killall mDNSResponderHelper
        dscacheutil -flushcache
        ;;
    # macOS 11.0 -- Big Sur and Monterey, when in compatibility mode show up as "10.16". (SYSTEM_VERSION_COMPAT=1)
    10\.16*)
        echo "Flushing DNS cache for macOS 10.16 (11 & 12 in compatibility mode)"

        sudo killall -TERM mDNSResponderHelper
        sudo killall -TERM mDNSResponder
        dscacheutil -flushcache
        ;;
    # macOS 11.0 12.x -- Big Sur, Monterey, Ventura, Sonoma, and Sequoia
    11\.*|12\.*|13\.*|14\.*|15\.*)
        echo "Flushing DNS cache for macOS 11-15.*"

        sudo killall -TERM mDNSResponderHelper
        sudo killall -TERM mDNSResponder
        dscacheutil -flushcache
        ;;
    # macOS 26.x -- Tahoe
    26\.*)
        echo "Flushing DNS cache for macOS 26.*"

        sudo killall -TERM mDNSResponderHelper
        sudo killall -TERM mDNSResponder
        dscacheutil -flushcache
        ;;

    # Catch anything else...
    *)
        echo "Sorry, this script is not prepared to handle your version of OS X / macOS."
        exit 1
esac

echo "DNS cache flushed."

exit 0

Updated through macOS Tahoe

it has been a while, but here is my favorite script updated all the way through Tahoe