DNS Lookup Time

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Created: August 15th 2015

What is DNS Lookup Time?

  • DNS time is the amount of time it takes a domain lookup to occur while a browser retrieves a resource.
a dns lookup and clocks

It can be calculated using domainLookupEnd - domainLookupStart from the Navigation timing API 1.

What are DNS lookups?

  • DNS stands for "Domain name system"
  • Domain names like "varvy.com" must be mapped to an ip address to be found
  • The DNS lookup is a request to another server requesting the ip address for a certain domain name
dns lookup

Why is DNS Lookup Time measured?

DNS lookups can cause significant delays in rendering a webpage.

Understanding the time taken on DNS lookups not only provides a more accurate understanding of user experience, it also can help motivate decision makers / webmasters to use DNS lookups wisely.

How to improve DNS lookup time

  • Minimize DNS lookups overall.
  • Call resources from the same domain as the HTML was called.
  • Use a solid, well known registar with built in quality DNS services.
  • Consider outsourcing DNS services.

Minimize DNS lookups

Every third party resource used on a webpage (tracking, analytics, social buttons, etc.) adds a DNS lookup. This is bad. It is not uncommon for a page to have 5 to 15 DNS lookups which have nothing to do with the actual page content. This scenario can be optimized for, however it requires a good understanding of your pages, what they are calling, and what your goals are. Learn more about minimizing DNS lookups.

Call resources from the same version of url as the HTML was called.

Ensure page resources like CSS, Javascript, images, etc. are being called from the same domain, using the same url structure. Using relative links for resources removes any risk of causing unintended / unnecessary DNS lookups.

Use a solid, well known registar with built in quality DNS services

Consider using a well known registar that you trust.

I use Google domains and their provided DNS name servers.

Consider outsourcing DNS services

Using a third party for your DNS services can be a smart move. Consider using Google Cloud DNS or another with a name that is recognizable and that you trust.

Patrick Sexton by