TTL – Definition and Best Practices

What is the definition behind TTL?

TTL, also referred to as time to live, is a setting that is frequently used to specify how long a DNS record should stay in a DNS resolver’s cache. Using TTL makes websites faster since they can be received more quickly if the DNS lookup has already been cached locally rather than needing to go through the complete lookup procedure on a DNS server.

Caching DNS records is undoubtedly very helpful for increasing speeds and lowering the strain that DNS resolvers worldwide endure. Setting your Time to live too high, however, can lead to problems. For instance, if a DNS record needs to be changed, the change won’t go into effect until the TTL has passed. The propagation period is what we refer to as this.

TTL and DNS – What you need to know

The TTL (time to live) of a DNS record, such as an A record or an ALIAS record, specifies how long it will be valid (in seconds) and how long a nameserver (a recursive or secondary DNS server) can hold it in its cache memory. The DNS record will be removed when the Time to live reaches zero.

To achieve the record from a recursive DNS server, the DNS client must query the server again and wait for it to generate a new DNS query. Then, depending on the TTL, it will be cached again.

Before updating its DNS records, a secondary DNS server should confirm with the primary DNS server and complete a zone transfer. It won’t be capable of responding to queries about the domain if it doesn’t.

Time to live and defense against DDoS attacks

TTL is the means to prevent website name requests for DNS records from continually circling (hopping) server networks now that the web is truly global. It would be similar to running your electricity but never turning off a switch to allow unlimited inquiries.

This expensive process of circling a query is known as “looping.” Because of this, servers’ overload,’ which makes them susceptible to data hacks. Your uptime can be protected by TTL, reducing the time allotted for the ask and re-ask and the number of hops allowed to query the DNS server.

Cybercriminals plan assaults on the Internet’s DNS layer because they want information. DNS query assaults also referred to as Distributed Denial of Service (DDoS), keep a server busy by repeatedly requesting that the name of your website be resolved (a DNS resolver forwards query).

Best practices for implementing TTL

TTL is a time interval that is calculated in seconds. The most typical default values are 1 hour (3600 seconds), 12 hours (43200 seconds), or 24 hours (86400 seconds). This means that the new DNS updates will take 1/ 12 or 24 hours to take effect if you move a website to a new server or add a unique URL to your server.

You should use a short TTL number if you intend to make DNS updates soon. This is done to hasten the propagation and recognition of modifications made to the Internet. The minimum DNS TTL value should be raised from 0 to a positive integer, in other words. Additionally, it must never be made zero. It is not specified in the standard and could result in rejection or disregarding your DNS information.

Additionally, 604800 is the maximum DNS Time to live value (7 days). No maximum DNS TTL value exists, although values larger than 7 days are rounded to 7 days.

So, when determining Time to Live (TTL), keep the following essential factors in mind:

  • The longer the TTL, the fewer times caching name servers must query authoritative name servers.
  • A longer Time to live reduces a site’s perceived latency and its reliance on authoritative name servers.
  • The shorter the TTL, the faster the cached record will expire. This enables more frequent queries for the records.


Thanks to the International Networking Working Group, we use TTL for more than 40 years. Time to live, usually referring to as TTL or Hop Limit, is a system that restricts how long data can survive in a computer or network. TTL can be applied as a timestamp or counter that is either connected to or built into the data. So, it’s absolutely something that you need to know. 

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