The top site speed mistakes crippling eCommerce conversion

Research from Kaizen looks into how 700 of the top eCommerce companies in the UK optimise for site speed across desktop and mobile – or in some cases, how they don’t. Find out how they’re missing out on CRO opportunities and how you can avoid making the same mistakes.

When building an eCommerce site to sell your product or service, there are a number of factors to take into consideration – branding, functionality, user journey often foremost among them.

But one feature that goes unprioritised all too frequently is the site speed. Although a delay of as little as a second when loading a page can cause a 7 per cent reduction in conversion rate (and a speed improvement by one second can provide a 27 per cent conversion rate increase), a large proportion of top eCommerce sites are failing to make worthwhile efforts to improve their efficacy.

Looking at the Google PageSpeed, HTTP/2, load time, and the size of the homepage of 700 websites, selected by top monthly traffic as reported by SimilarWeb, Kaizen have produced a new whitepaper that not only highlights some of the most surprising limitations of these sites – such as desktop sites being 9 per cent better optimised than mobiles on average, despite 51 per cent of traffic being from mobile devices, compared to 42 per cent on desktops (with the remainder from being other connected devices) – it also provides a number of suggestions, tips, and approaches on how to counter those errors and update any site to a modern age, with statistics highlighting the advantages.

In the case of HTTP/2, for example, saw customers’ average page load time nearly halved when they implemented HTTP/2, changing from 9.07 seconds for to just 4.27 seconds for HTTP/2. And many websites could lower their loading times by reducing their size – as the average eCommerce site size is 35% bigger than the wider average, at 3.1 MB. For reference, that’s bigger than the shareware version of the classic video game Doom – only 2.3 MB.

The top 10 eCommerce sites for speed

Of the 700 eCommerce sites researched, the following scored highest when it came to speed, across the four factors:

Rank URL Desktop Score Mobile Score Page Size (MB) Average Load Time per MB HTTP/2 Final Score
1 97 96 2.8 0.9 N 9.77
2 96 95 2.9 1.7 N 9.65
3 98 98 3.5 0.67 N 9.53
4 95 94 0.9 1.74 N 9.4
5 97 95 2.7 1.17 N 9.4
6 87 95 2.6 1.29 Y 9.11
7 89 88 0.7 1.62 Y 9.07
8 93 90 5.2 0.83 N 9.05
9 82 94 2.7 0.47 N 8.99
10 88 86 1.1 0.77 N 8.98

Un-break the internet

If you’re seeing some mistakes that you’ve already made with your own site, here are a few ways to ensure you bring your page speeds to the minimum possible, including:

  • Browser caching – Resources can often be loaded from the cache, improving site speed for returning visitors who have loaded the page once already, and especially for frequent visitors (i.e. your loyal customers).
  • External JavaScript loading – Larger JavaScript blocks should also be put into a .js file and loaded externally to the main page load, allowing the browser to load the resources with more efficiency and allows the browsers to utilise their cache.
  • Google AMP – Google AMP pages are preferred by Google in search rankings, and are faster to load. Though it’s still a developing technology, it can be a time saver and SEO booster for any eCommerce company.
  • Tag Audits – Regular audits of existing tagging strategy can save vital microseconds: on one site researched, 14% existing tags were still installed with active triggers despite being obsolete and/or redundant.

Mobile management

It wasn’t just general speed that was an issue across all the sites – one of the biggest concerns for eCommerce businesses should be their mobile customers.

The Co-operative, one of the top sites researched, receive only 35.25 per cent of their traffic from desktop, with 64.75 per cent coming from mobile devices – a trend reflected across most of the rest of the industry. And while 20 per cent of the sites serve their mobile users a separate mobile site, this is sub-optimal when compared to a responsive site option, used on only 80 per cent of sites.

And what’s worse, many of the mobile sites that were on offer were poorly-optimised for mobile, with the average mobile site scoring 55/100 for speed, as opposed to the average desktop score of 60/100.

Praseeda Nair

Kellen Rempel

Praseeda was Editor for from 2016 to 2018.

Related Topics

Tech Jobs & Careers