Web Performance
Website performance: why does it matter?
Last updated 20 April 2020

As web developers, we are often asked to perform website performance audits and optimisations. And for good reasons: website performance plays a major role in the success of an online venture and it impacts many elements such as SEO, User Experience and Conversions.

A better first impression

A website that loads faster is more likely to give a better first impression to users. This is key as often, this is also the first impression that customers will have of a brand.

It has been demonstrated that slow web pages lower perceived credibility (Fogg et al. 2001) and quality (Bouch, Kuchinsky, and Bhatti 2000).

On top of this, if a website is too slow to load, users are more likely to leave the website immediately.


This behaviour is reflected in the bounce rate that can be measured with tools such as Google Analytics.

The bounce rate is defined as the percentage of users that leave a website after viewing only one page.

Pages that load within two seconds have an average bounce rate of 9%, while pages that take five seconds to load have a bounce rate of 38% according to a research by Pingdom.


Another research by Google shows that 53% of mobile users will leave after 3 seconds. Given that more than half of the worldwide web traffic is generated through a mobile phone, the mobile load time is particularly important.

A more engaging user experience

The user experience is directly tied to the website performance and a website that performs better is more likely to see increased engagement from its users. On the other end, performance bottlenecks such as slow loading of images have a negative impact. For example, research shows that 39% of people will stop engaging with a website if images won’t load or take too long to load.


The following technical indicators can be used to identify potential performance bottlenecks which could hinder the User Experience:

  • UX Analysis and User Testing

  • Usability Testing

  • Page Views - How many pages are browsed by the users?

  • Behaviour Flows - What path did the users follow on the website?

  • Timings - How long does it take for users to fill out a form or perform an action on the website?

For a complete performance review, user experience testing should be carried across different devices (mobile, tablet, desktop) and under different network conditions. A website that performs well for a given user on a desktop device could be underperforming for another user on a mobile and the analysis should review as many scenarios as possible to identify bottlenecks and opportunities.


Here again, delivering a fast and engaging mobile user experience is key. According to Google, 61% of users are unlikely to return to a site on mobile if they had trouble accessing it and 40% visit a competitor’s site instead.

Better Ranking in the Search Engines

Finally, websites that perform better are more likely to rank better in search engine results pages as website speed is a ranking factor for desktop and mobile searches. Search engines such as Google reward website with a better performance and this is now an essential aspect of the technical optimisation for SEO.

Read more

This article is part of a series about website performance. 

More information on how to measure the performance of a website can be found in our articles about measuring website performance. The main technical optimisations techniques are covered in our website performance optimisation article.