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How to flush the DNS cache in Mac OS X & macOS

By 6 comments Last updated March 15, 2017

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This short article describes how to flush (or reset) the DNS cache. DNS queries (IP addresses) are usually cached, but sometimes it may be necessary to empty and flush the DNS cache. Clearing (or “flushing”) cache refreshes this data. For instance, if you experience a lot of 404 (cannot find server) error codes or you encounter issues where the named server is not resolving properly, you may want to reset your DNS cache. Luckily, this process is really easy.

How to flush the DNS cache in Mac OS X

About Your Mac’s DNS Cache

macOS and OS X keep a local cache of resolved DNS queries for a time specified by the DNS server. Sometimes it’s necessary to reset the cache immediately and re-query a DNS server. For example, if your DNS server has recently changed, you might need to do this.

If your Mac isn’t using the latest DNS entries from your server, restarting your Mac usually updates its cached information. If you want to update DNS entries and you can’t restart your Mac or Server using macOS or OS X, use the terminal commands below (dependent on macOS or OS X version.)

Flush the DNS cache in macOS Sierra and different Mac OS X versions

macOS Sierra

Open Terminal and enter the command below. This command clears MDNS and UDNS caches. DNS in macOS is handled through mDNSResponder, killing the process is the easiest way to reset your DNS cache on a Mac aside from rebooting and manually changing DNS settings. Remember that when prompted to enter a password, enter your Mac login password and hit Enter.

sudo killall -HUP mDNSResponder

The command sudo dscacheutil -flushcache also works


Flush the DNS Cache macOS Sierra & mac OS X

OS X 10.10 Yosemite & El Capitan

Use the following Terminal command to reset the DNS cache in OS X v10.10.4 or later

sudo killall -HUP mDNSResponder

Use the following Terminal command to reset the DNS cache in OS X v10.10 through v10.10.3

sudo discoveryutil mdnsflushcache

Enter your admin password when prompted to perform the flush.

OS X 10.9 Mavericks

Open Terminal and enter:

dscacheutil -flushcache;sudo killall -HUP mDNSResponder

OS X Mountain Lion or Lion (10.7 and 10.8)

Launch the Terminal app (Applications > Utilities > Terminal) and enter (put in your admin password when prompted):

sudo killall -HUP mDNSResponder

Mac OS X 10.6 and 10.5

Open Terminal and type:

sudo dscacheutil -flushcache

Mac OSX 10.4 And Below

Launch Terminal and enter:

lookupd -flushcache

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Verify Your DNS Issues Are Resolved

To check whether your DNS is now working normally, use the “dig” command. Stay in Terminal and type “dig appletoolbox.com.” Or the name of any website you regularly visit–just make sure you type dig before the web address.

The command dig is used for querying DNS name servers for information about host addresses, mail exchanges, nameservers, and related information. If speed is your issue, look under the ANSWER SECTION for the Query time.

Flush the DNS Cache macOS Sierra & mac OS X

If that number proves too high, meaning it’s taking too long for the site to load, change your computer’s, devices’, or router’s DNS settings to Open DNS Servers (208.67.222.222 & 208.67.220.220)or Google Public DNS Servers (8.8.8.8 and 8.8.4.4.)

Save a .scpt File to Your Desktop for Quick Access

  • Open “Script Editor” and add the following command and then save to your desktop (copy and paste the following line including quotes)
    • For macOS Sierra, do shell script “sudo killall -HUP mDNSResponder”
    • For El Capitan, do shell script “sudo dscacheutil-flushcache; sudo killall -HUP mDNSResponder”
  • Double-click that file anytime you need to flush the DNS
  • If you want a message in Terminal letting you know that the DNS was flushed add the following command to your line
    • ;say DNS cache was successfully flushed

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  1. mDNS says

    I located this ip 184.105.247.203 connected. To the mDNSresponder on a MacBook Pro, associated with hundreds of complaints. One person said they hacked and changed his Facebook account password. If they can see that. Imagine all the private photos and messages they hack into.

    Reply

  2. Stacy says

    This works for flushing the DNS cache, but if you want to view the DNS cache on macOS Sierra, run:
    sudo killall -INFO mDNSResponder

    and it would dump the cache into the Console app.

    Reply

  4. Jan says

    I can’t get anything on my safari so I’m trying your suggestion. When I open Terminal and enter your command nothing happens. Is a password required and if so when?
    Thanks for your help!
    Jan

    Reply

  6. An4nas says

    Continuation ……. few questions,

    1- What is the best/fastest way to learn Bash shell
    2- Have you got more security codes, to either amplify or reduce whatever it might be
    using terminal…. ex: How can you control ports being used without your permission,
    and to disable them!
    3- How to be able to see who snooping, or what could be regarded as so, and then block those
    re-enabling files that keep on generating it’s self, ex: I’ve got a few: .plist preferences files,
    that keep on re-appearing after secure deletion….or files that are invisible to you (The Administrator!!) and are not allowed access to!

    Thanks in advance….

    Reply