What are Time to Live (TTL) values?

Time To Live (TTL) values are given to DNS records to tell servers how long their caches should be kept before new ones are fetched.

These values are important as they affect the amount of time it takes for a DNS update to take place as well as the amount of time required to resolve a DNS record.

When your browser requests a web site, the location is looked up through the following process:

1. The requesting computer checks itself for cached DNS records for that domain.  The locally cached records helps speed up the resolution time, resulting in a faster loading page.
2. If there are no locally cached records, the computer consults the nearest nameservers in the network for these records. These nameservers usually belong to the Internet Service Provider.
3. If there are no cached records, the designated nameservers for the domain are consulted to find the appropriate A or CNAME record for the website.

When you change information on your DNS records, you change the information on the designated nameservers, but the other nameservers and computers around the world have cached records and will not be until their Time To Live value is reached and they fetch the latest records from your nameserver.

This process can take up to 24 hours when the standard TTL values are used, so it can take a while before the updated DNS records filter down thoroughly.

Article ID: 219
Created On: Tue, Mar 10, 2015 at 5:20 PM
Last Updated On: Thu, Aug 10, 2023 at 1:08 PM

Online URL: https://www.heartinternet.uk/support/article/what-are-time-to-live-ttl-values.html