TTL is a setting for each DNS record that specifies how long a DNS resolver on the internet caches, or remembers, the DNS settings before they expire and a new query needs to be done.
TTL in DNS records is specified as a number of seconds. When a DNS resolver has retrieved the required information from our DNS servers, it caches that information for the specified TTL number of seconds. Once that period of time has passed, the DNS resolver will need to contact our DNS server again to get the current DNS information for the domain.
The benefits of a longer caching time are that it is much faster to check your local resolver’s cache than having to do a look up of the DNS records via the DNS server so this results in a faster experience when browsing and also greatly reduce internet traffic – for our DNS servers and also for the internet generally !
The potential problem with having a long TTL setting is that if your Internet Service Provider has the current IP address for your website cached for say 24 hours (86400 seconds), it won’t check for a DNS update for your domain until that 24 hours has passed, even if a DNS change for that domain was made 5 minutes ago for example as a result of moving to a new hosting provider.
For this reason, if you are going to move your website from a different hosting provider over to us, you may want to lower your TTL on your domains (to say 300 which is 5 minutes) before changing the nameservers to point to us. If your TTL is currently set to 86400 then you need to do this at least the same amount of time before you do the change. If you dont do this, then this is when you get situations where some people are seeing your website on the old server and some are seeing it on our new server – this entirely depends on how when the DNS resolver that your ISP is using gets updated. It could be 23 1/2 hours after the move or they could update 2 minutes after you make the change. Be sure to change the TTL back after the move has been completed !