DNS (Domain Name Server) is the next thing after domain registration and web hosting package purchased from a web hosting provider and the websites files are uploaded onto a server. Once all these tasks are completed it takes time for the DNS to get propagated.
There has been a common question raised by most of the clients when DNS propagation is executed. But, before explaining about DNS propagation, it is important to get yourself educated about how DNS works. When a website is set-up on the server of a web hosting provider, a Master DNS record is created in the Domain Name Server (DNS). The Domain Registrar points to your web hosting providers DNS server as they are the master authority of your domain. When a visitor is in search of some information/service/product that is available on your website, the request first of-all goes to the registration database to find out who the DNS authority is for your website. Then getting information from there it points to your hosting providers DNS servers to get information of IP address assigned to your web site. This way the visitor is in a position to view your website.
The problem in this complete procedure is that, in order to fasten the rate at which the visitor can view the Internet, every ISP(Internet Service Provider) caches their DNS records. With this it means that they make their own copy of master records. And hence read from them locally instead of looking from the Internet everytime a visitor wants to view your website. This method is used to improve the speed of internet surfing.
Each company or ISP who caches the DNS records updates them after every few days, henceforth, delaying the time taken by your website to be viewed by others over the Internet. There isn’t any standard interval set by web hosts, they can set the time between some hours to many days. This slow updation of servers cache is known as propagation, as your websites information of the DNS gets propagated across all the DNS servers over the web. As the cache time is different for all the severs, it may take anywhere between 24 to 48 hours maximum (at ideal conditions) for the DNS changes to be applied.