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Prefetching DNS using rel=”dns-prefetch”

pre-feteching

In this article I will show you how to resolve DNS before a webpage is actually requested by the browser. Before you continue with this article please read my article on preloading resources and prerendering recourses. In that article I explained critical time, caching requirement and many other basic concepts which will be used in this article.

What is DNS Resolution?

Dns resolution is a process of converting a domain/hostname to an ip address required to access a resource (this process is what converts a user friendly url like: http://qnimate.com to http://85.72.179.121 ); this requires a certain time and adds to the page loading process. Dns resolution takes very less time and bandwidth therefore pre-fetching large number of domain names will not harm user experience.

How to pre-fetch DNS?

We can pre-fetch DNS by using the rel=”dns-prefetch” attribute on the link tag.

<!-- Here DNS resolution for qscutter.com domain will be done before the page is requested. -->
<link rel='dns-prefetch' href='http://qscutter.com'>

A content provided(HTTP response) can force the browser not to DNS prefetch for the domain by using the x-dns-prefetch-control: HTTP header assigned to “off”.

This response domain name will not be pre-fetched.

x-dns-prefetch-control: off

You can again enable by setting the same response to “on”.

Narayan Prusty
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Comments: 1
  1. 5 years ago

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Narayan Prusty

I am a software engineer specialising in Blockchain, DevOps and Go/JavaScript. This is my personal blog where I write about things that I learn and feel interesting to share.

Image8 years ago 1 Comment Web Development
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