You might have heard your website developers say you need to “wait for the DNS to propagate” before you see a new website go live. But… What is DNS and why does it propagate?

Every device on the internet is identified by a unique number, like a telephone number, called an IP address.

So the computer which run this website’s IP address is 139.162.206.87. If you wanted to, you could access this website by typing 139.162.206.87 into the address bar – try it!

To continue the telephone analogy, DNS (or a Domain Name Server) acts as phone directory for the entire world. Every time you type a URL such as “indiespring.com” for example, your browser contacts one of hundreds of global DNS servers asking for the relevant IP address, just like when you look up a phone number in the directory. Once your browser has the IP address it then knows which server to talk to when fetching the website.

Without DNS, you would need to remember every website’s IP address in order to access it. With DNS you only need to remember the URL – indiespring.com – much easier!

So what is a DNS propagation?

Often, when putting a new website live, developers will load the new website onto a new server so they can get it ready without interrupting the old one. Once you are ready to go live they update the ip address of the website so people will go to the new website instead of the old one. This change needs to be made to hundreds of servers around the world which constantly update themselves from each other. This process is called propagation – the time it takes for every copy of the internet’s phone book to update itself so people are directed to the new website, not the old one.