You've probably heard the term "DNS propagation" before, but aren't quite sure what it means. Don't worry, you're not alone. Simply speaking DNS propagation is the time period it takes for any changes made to your domain to be in full effect across all servers on the internet. Such propagation will occur after any:
1. Changes to your domain’s WHOIS information.
WHOIS is a publicly available tool that searches the databases of domain registries and registrars to detail the domain owner contact information. A change to your WHOIS information (such as updating your contact details) can take up to 72 hours to propagate fully.
2. Changes to the DNS records or name servers of your domain.
Every time you use a domain name on your computer its DNS information will be stored in the cache. This can be local cache on your computer’s operating system, DNS cache stored by your Internet service provider, etc.
DNS records are stored in cache mainly to improve the performance of DNS queries. Every DNS record has a Time to Live (TTL) value, which is the time DNS servers should store that record in the cache. Even if a record is changed, DNS servers will continue working with its formal value from cache until this time has passed.
This is the essence of DNS propagation – it is the time required for DNS servers worldwide to update their cached information for a domain name. It is influenced by the TTL of DNS records that might have changed, but there are also other factors that could come into play.
A DNS change requires up to 72 hours to propagate worldwide, although most often this happens in a matter of hours.
Learn More about DNS Propagation
DNS propagation is a complicated subject, and to fully understand it you need to know how the internet works.
Let's start with DNS, which stands for "domain name system." A domain name, such as "your-domain-name.com," is an easy-to-remember name that is associated with an IP (internet protocol) address such as 173.194.46.41. While it's easier to remember google.com rather than 173.194.46.41, the internet works on IP addresses. Just like every house has a unique street address, every website is associated with a unique IP address. So when I open up my browser and go to google.com, it's really just going to 173.194.46.41.
Now let's move on to how your browser knows that google.com is associated to the IP address 173.194.46.41. This is the part where you need to understand more about how the internet works. Your website lives on a web server (which is just a beefed-up computer set up to specifically run websites) in a data center somewhere in the world and the web server will have one or several IP addresses used to find it.
In addition to these web servers, thousands of DNS servers are located around the world. The sole responsibility of a DNS server is to take domain names and associate them to an IP address. These DNS servers store records for every domain and its IP address so that when you type google.com into your browser, it knows to take you to 173.194.46.41, which is the address to the web server where the website is hosted.
So, how does DNS propagation fit into this? It's quite simple actually. When DNS changes are made (like switching hosting providers or switching from an old website to a new one) every DNS server in the world needs to update its records of what IP is associated with which domains. You can imagine it takes some time for every DNS server in the world to update its records. So until they all update to the new DNS/IP information, one might have the old info while another might have the new info.
Let's say we are launching a new site called xyz.com on a different web server and we update the DNS records. Let's also say that the DNS server I use has updated with the new information, so when I go to xyz.com I see the new site. But the DNS server you use hasn't updated, so you go to xyz.com and see the old site. This is because the new DNS updates haven't propagated yet to the DNS server you are using.
It's simply just the time it takes for all the DNS servers around the world to catch up with the new DNS updates. It's also why all of us web nerds say that it will take one to 24 hours for DNS propagation.
