www.example.comdoes not open (or vice versa).
In system DNS there is a situation when a server caches data and the state of the domain for a certain period, specified by TTL (time-to-live) or within the server itself, after which the information is updated. The maximum cache time can be up to 72 hours. Such caching can be encountered when NS servers, A (Ip to which the domain is directed) or other records have been changed, as well as after registering or restoring a domain.
How the Internet Domain Name System works:
Before registering a domain name, you enter the domain name
example.com on your device. The following operations take place:
Some time passes and you fill out an application on our website for domain name registration... We send you a notification that the domain has been registered. You enter the domain address on your device, but you still get the answer that no such domain was found. This is due to the fact that now there are operations that differ from those that took place at the beginning, namely:
example.com... This is due to the fact that DNS-the ISP's server remembered that there is no such domain, and it will remember it from 1 to 24 hours.
A similar situation occurs when changing domain records, but unlike the previous one - the answer from DNS- domain zone servers (.COM or others) comes with an indication of the server that hosts the domain records of the requested address, most often it is the provider's NS server. In this case, the procedure for obtaining records for the domain example.com approximately as follows:
Subsequent retrieval of information is done either by providing a cached response, or by making all requests anew. But clear the cache DNS-servers of Internet providers is simply impossible, you just have to wait for their independent update.