Flushing the DNS cache causes the computer to erase stored IP addresses and query servers for new information. The DNS cache allows computers to keep pages updated and synchronized with each other. Clearing the DNS cache becomes necessary when a large number of HTML 404 error codes appear or the cache is poisoned due to a virus or glitch.
Sometimes referred to as "the phone book of the Internet," the DNS helps direct web traffic by providing computers with access to a database of network names and addresses. It translates a given URL into the server's IP address, allowing people to access websites without memorizing a string of numbers. The DNS cache is a local copy of recently accessed IP addresses that prevents queries from constantly traveling up and down the server hierarchy, speeding up loading times.
In addition to malfunctions caused by malware and glitches, network connectivity issues can often be traced back to a poisoned or outdated cache. As of 2014, both Windows and Macs allow users to flush the cache manually by inputting either the command "ipconfig /flushdns" or "sudo killall -HUP mDNSResponder" respectively. For older Macs, users have to run the command "sudo dscacheutil -flushcache" instead.