DNS propagation is the process of applying DNS record updates across all servers on the internet. Nameservers cache domain record information for a limited amount of time before refreshing, so record changes do not take effect immediately.
DNS propagation often takes a couple of hours, but it can take up to 72 hours. The propagation timescale depends on several factors, including the internet service provider (ISP), the domain's registry, and the DNS Time to Live (TTL) values. Although carefully scheduled record changes will not cause domain downtime, visitors may still see a cached version of the website until DNS propagation is complete.