DNS lookups are the process by which IP address lookups (e.g. converting google.com to an IP address like 72.14.204.99). This enables the use of easy to remember domain names rather than IP addresses for visiting your favourite web sites, sending email to people and so on.

DNS is an integral part of how the Internet works, and almost everything you do online makes at least one DNS lookup. Because so many DNS lookups happen, there is some “caching” or remembering of the answers for a period of time to improve the overall efficiency and speed of the system.

How long does the cache persist?

The length of time a DNS result is cached depends on the value known as the “time to live” (TTL) set by the authoritative DNS server for the domain.