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 again for El Capitan through Monterey - Big Sur and Monterey include compatibility mode recognition too. (10.16)

I have been maintaining this script for some time, but I have been forgetting to update the gist. I have included the gist in the comments near the version, so that in the future, I will hopefully remember to update the gist when incrementing the version.

Updated to include Ventura

Look at that, including the link to the gist last year made me remember to update the gist this year!

Updated through macOS Tahoe

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