How to view DNS cache in OSX?

mDNSResponder (multicast DNS daemon) SIGINFO signal can dump a snapshot summary of the internal state to /var/log/system.log, including the cache details. To do this:

Keep system log opened in one terminal:

tail -f /private/var/log/system.log

Send a SIGINFO signal to mDNSResponder from another terminal:

sudo killall -INFO mDNSResponder

Then check the logs in first terminal, you would be able to see cache dump:

mDNSResponder[98]: ------------ Cache -------------
mDNSResponder[98]: Slt Q     TTL if     U Type rdlen
mDNSResponder[98]:  52      1827 -U-      CNAME   17 www.sublimetext.com. CNAME sublimetext.com.
...
...
mDNSResponder[98]: Cache currently contains 154 entities; 3 referenced by active questions

(For more info: man mDNSResponder)

As @PrasseethaKR and @kjagiello point out, on High Siera mDNSResponer has moved from syslog to log. In addition, your DNS lookup messages are now considered private and will show as <private> in both Console and log stream by default.

To view your DNS lookups on High Sierra open an Terminal and run:

sudo log config --mode "private_data:on"
log stream --predicate 'process == "mDNSResponder"' --info

To go back to using private just run the following command.

sudo log config --mode "private_data:off"

Cheers!