DNS timeout failure on MacOS
Flush DNS cache. Clear corrupt DNS cache. Fix domain name resolution timeout errors.
Sometimes Safari and Chrome browsers will start to load a page but then never finish. The problem does not seem to affect all pages. The problem seems to especially affect Google applications such as Gmail. Rebooting does not seem to clear the problem. The source of the fault is an uncommon failure in the name resolution service that MacOS uses. The local DNS cache may be corrupted for an unknown reason. It's not clear why pages seem to partially load and then timeout. The problem seems to be with the mDNSResponder service, which provides support for zeroconf (Bonjour).
The fix is simple. Open a command-line shell and enter the following command:
sudo killall -HUP mDNSResponder
This will tell the mDNSResponder service to flush the cache and reload the service.