7 Page Speed Killers that Cost You Conversions

A look at how page speed affects conversion, and why you should ignore Average Page Speed!

4 Jason Ford

We all know that your Conversion Rate is intrinsically linked to Page Speed; but do you know why? We’ve all read the shock stats such as:

There are many pages out there which demonstrate the same findings, that a quicker site leads to more conversions. Whether that is by citing others research (as we’re doing here), or by providing their own case studies (like our OPI Page Speed Case Study and Andrew Martin Speed Improvement), there is lots of evidence to demonstrate you should be looking at Page Speed for to improve your Lead Generation or Conversion Rate.

What you’ve been doing wrong, and what to do to correct it

1. Ignore Average Page Speed; and start measuring Percentile Load Times

Average Page Speed is a pretty useless metric on its own, and it also provides misleading information about your customers experience.

The average page speed in Google Analytics is the Mean (the sum of all values divided by number of values), which hides critical information such as how distributed the page speed is.

The Mean is also susceptible to outliers, especially when considering something like page speed (where you’re aiming for lower numbers). For example, a single Page Load of 50 seconds, contributes just as much to the sum as 50 Page Loads at 1 second, which can drastically skew the average.

There are plenty of resources that explain the limitations of averages, and how they’re affected by distribution.

Page view chart

2. Stop ignoring quick fix browser improvements

There are hundreds of blogs and articles out there which all list essentially the same things, and yet there are plenty of websites not using these quick fixes to improve their page speed, and therefore the number of leads or conversions they’re getting:

  • Merge, Minify and Compress CSS & JavaScript
  • Resize and compress every image properly using a service like TinyPNG
  • Enabled GZIP and HTTP-2 on your server
  • Use Google Tag Manager for all your tracking and additional scripts (like Facebook Pixel, etc)
  • Use a CDN like CloudFront for static files
  • Use Chrome’s Developer Tools to see what is actually being loaded on your pages.
Panda saving image

3. Set a budget for improving Page Speed

It’s not as visual as changing the colours on your website, but speed actually has such a sweeping affect on all customer metrics, you should set a proportion of your Web/Marketing budget specifically for improving performance.

Whilst there are a lot of best practices, Magento and WordPress are complicated systems with many 1,000’s of files, and over half a billion lines of code, combine that with your data and customers being completely unique, you need to optimise your site individually.

Getting a Speed & Performance Audit and then prioritise getting the most out of your Lead Generation or Ecommerce Checkout, but make it an ongoing process to keep refining and improving.

4. Think of Page Speed as Customer Satisfaction

We often get the question ‘How fast should my page load?’, and it’s a great question. Should you be aiming for 1 second, 2 seconds, 3 seconds? Should all your customers be under your target?

All good things to consider, and it really does depend on your customers and your customers expectations, as well as things like budget.

  • If your business is 90% a UK business, then set targets for ‘inside the UK’ and ‘International’
  • If your business is 70% mobile devices, segment those users and monitor them separately
  • Segment the ‘types’ of pages, to see if your form pages are slower than they should be

Once you’ve got a good idea of the groups your looking at, see what speed your Converters have, this should give you an idea what you’re looking to achieve. Aim for 80-90% of a segment to achieve its individual target speed.

There is a simple methodology called Apdex, which is an industry open standard that defines a standardised method to report, benchmark and track application performance.

It converts many measurements into one number on a uniform scale of 0-to-1 (0 = no users satisfied, 1 = all users satisfied).

5. Don’t believe the ‘Silver Bullet’ approach

Silver Bullet approach is something which presumes to provide an immediate solution to a problem, much like ‘waving a magic wand’.

Unfortunately, like many things in this world, these are often too good to be true, and have a quite drastic negative side, that isn’t always apparent at the time.

There are some great examples of this, especially with large enterprise websites which can be quite resource intensive and expensive to run (see below).


CloudFlare is a similar thing to Varnish, except instead of being at a server level, it is a completely separate network that sites in-between your site and your user. Although one of its key points is defending against DDoS attacks, it also boasts to be a lot quicker.

However, this does come at a cost, which a lot of people have run into. You now have an additional point of failure for your website. If CloudFlare goes down, or more likely there is an issue with CloudFlare communicating with your website the user gets an error message like this.

Not exactly user friendly, and also completely unbranded, which is such a poor experience.

error 522 image

Varnish Caching

Varnish Caching is a server level caching solution, which intercepts all of your server requests and tries to serve them from its own storage before resorting to the application itself. It’s commonly deployed with Magento.

In most cases, this is used to mask the issues with how the application has been adapted or modified, instead of solving the real problem.

Varnish is also a complicated system as it needs to know which parts of the page can be cached, and which bits are custom to that user (e.g. the basket on an ecommerce site). It also means that whilst the caches are ‘warmed up’, that the site will be working really hard and customers will be experiencing the slow effect anyway.

Varnish should be the ‘icing on the cake’.

6. Don’t break UX in the search of Speed

Like everything on your website, if you want to convert those leads, make sure that you’re putting the user first! The User Experience (UX) should be considered in everything you do, including Page Speed, SEO, Design, Content and Branding.

If you’re reducing your images sizes drastically, does that mean you’re also losing quality, which means customers will have a worse experience?

Do you have a Flash of Un-styled Content (FOUC) which causes customers issues?

If you delay functionality from loading, will the prevent the user doing something they’d expect when they see the page load?

7. Don’t always trust Google PageSpeed Insights!

Google provides a lot of amazing tools for free, such as Universal Analytics, and their Office Suite of tools.

However, one of their most misleading tools is their PageSpeed Insights. This tool scans a page on your website and gives you a checklist of things that will improve your page load times.

Let’s have a look at some websites that fail this test:

Please don’t take this the wrong way, a lot of what Google PageSpeed Insights recommends is valid, but what I’m suggesting is that it should not be followed blindly.

Understand that this tool is not a smart tool, and that you need to make up your own mind if it is worth doing.

For example, there might be situations like:

  • Compressing the images further will reduce quality too much
  • Don’t move CSS or JavaScript to the bottom of the page if it will impact UX
  • Optimisation starts to have diminishing returns; It takes twice as long to get half the page speed improvement.


Hopefully you’ve found the above useful for improving your Lead Generation and optimising your Page Speed in general.

If you’d like to discuss how we can help improve your website Page Speed, please get in touch and let we’ll be able to help you.