What Is DNS Propagation?

In order to function on the web, every domain such as yourdomain.com requires DNS, or the Domain Name System. Every time you go to a website, you actually go to the IP address associated with it and, with the the way how DNS works, there is no need to memorize this IP.

There are several types of DNS records that can be created for your domain and sometimes you may need to make changes to them. Due to the distributed nature of DNS records, any time such DNS changes are made (on any level), you need to wait for propagation to complete.

Detailed explanation of propagation:

  • You make a change to a DNS record associated with yourdomain.com: e.g. switch to another DNS hosting provider, update MX records, add a new CNAME record, etc.
  • Now this change needs to be cached by every DNS server in the world.
  • Until it is fully propagated, some of DNS servers might have the old cached information for your domain while others might already have the new one.

Note: a DNS change might require up to 72 hours to propagate worldwide, although most often this happens in a matter of hours.

How to check the propagation status:

In order to check the propagation status at several locations worldwide, you may use such online tools as What's My DNS?

 How is TTL related to the propagation time:

TTL, or Time to Live, is a specific parameter that is different for each DNS record. TTL defines the time DNS servers should store a DNS record in cache. In other words, it determines how often a DNS record get updated throughout the world. This parameter is defined in seconds and can be modified.

Notes:

  • Lowering the TTL value prior to making the DNS change will reduce the time for propagation, however, there is no exact answer on what TTL should be set to.
  • Keep in mind that the new TTL will have to propagate as any other parameter and will take old TTL+refresh.