DNS or the Domain Naming System is the backbone of the Internet.
Put simply, computers don't understand domain names (eg. www.coolexample.com). Instead computers work with IP Addresses (220.127.116.11). DNS is the system that looks up the friendly domain names we use and converts them to IP Addresses so our computers can locate the resources we need.
But what happens when we want to change the location of one of these resources, our website for example.
When this occurs we need to update the Domain Naming System so it points to the correct location. This is usually a straightforward process and is something we happily do for our web hosting clients, but the problem is it takes time.
The Domain Naming System is made up of a large number of servers located all over the world and it takes time for the changes we make to propagate to all of them. Usually between 24 and 48 hours. If we change the address of a resource it may be accessible to some but not all of our customers during this period of time.
So how do we know when our changes have propagated around the world?
Introducing What's My DNS?
Whatsmydns.net is a useful website for tracking DNS Propagation.
Simply enter the domain name you have updated and click the search button and Whatsmydns.net will show you the status from DNS servers around the world.