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The why of website optimisation: Increase site conversions

This is the first in a series of five posts where I'll outline the benefits that can be derived through website optimisation. Not only will we touch on monetary aspects, but we'll also get into environmental impact, and customer experience.

You can read the other posts in this series using the links below (they'll be at the end of this post too):

  1. Increase conversions (or engagement) - This post.
  2. Reduce operational costs​
  3. Reduce environmental impact​
  4. Improve your search ranking​
  5. Deliver a better user experience​

Now, let's get onto how optimising your website can help you improve conversions and/or engagement online.

The results speak for themselves

There's a wealth of evidence showing how even small performance improvements on individual, critical web pages can have a net positive impact on online sales & revenue.

One of the most famous case studies comes from Walmart.

Walmart saw up to a 2% increase in conversions for every 1 second of improvement in load time. Every 100ms improvement also resulted in up to a 1% increase in revenue.
~ Walmart, 2013

Over the years there have been many more example of companies boosting online revenue and engagement by delivering more performant websites. You can find a large collection of studies at Below are some more examples:

Zalando saw a 0.7% increase in revenue when they shaved 100ms off their load time.
~ Zalando, 2018
COOK increased conversion rate by 7% after cutting average page load time by 0.85 seconds. Bounce rate also fell by 7% and pages per session increased by 10%.
~ COOK, 2017

What pages should you optimise?

Ideally, you'd look to make optimisation wins across all pages on your website. However, at the bare minimum you should aim to optimise at least the pages that form your website visitor's critical path.

What's a critical path?

I use the term critical path to define the minimum series of pages that your website visitor would land on while completing a transaction, or engagement, on your website. This is easier to determine for an online store than it is for a content website.

An online store's critical path may look something like:

  1. Homepage
  2. Products listing pages
  3. Product details pages
  4. Shopping cart page
  5. Checkout page

You can determine the critical path for your website by thinking about what specific act you want website visitors to most perform. In the case of an online store, that's obviously making a purchase. A freelance writer might want to focus on getting visitors to contact them.

Where to start optimising?

As you can see from the examples above, focusing on optimising load time leads to better conversion and engagement results. To get started you can look at if you effectively use caching across your site. A proper caching strategy can help improve load times, especially if a user is going to be going through multiple pages of your site to complete a purchase. I have also covered other areas to look at in an earlier blog post A quick guide to easy web performance wins.

If you have a technical team on hand, then drop your web pages into Google's online Lighthouse testing tool. It will give you a digestible summary, as well as detailed suggestions on where you can improve the web page tested.