Site speed is absolutely critical. Not only can a slow website affect your SEO negatively, but it can also stop people buying from you. 

When we think of the UK's biggest retailers, we probably think about big web budgets, well resourced ecommerce teams and great technology designed to help them sell en masse to the Great British public. We might expect such sites to be great in terms of user experience, to be fast and work well on all devices.

But just how fast are they?

We took a look at the UK's top 50 retailers (according to this data from Retail Week) and assessed how fast they're performing during the busy Christmas Shopping season.

The Fastest and Slowest Retail Websites

Here's the overall list.

WH Smith was head and shoulders above the competition in our tests, performing consistently across its homepage and the category and product URLs we tested. Just WH Smith and Waitrose scored above 80 in our tests.

9 of the sites we tested scores below 40%. But, by some way, Pets at Home performed consistently poorest scoring an average of just 25.86% on the GTMetrix page speed test.

GTMetrix (and other tools we tried) were unable to run on the JDSports website.

So are the UK's retail websites fast?

On the whole, there's lots of space for improvement amongst most of the top retail sites we looked at. We also tested on desktop browsers on a fast connection, meaning we really were rather generous.

Big brands like these often have the benefit of being known and trusted, which goes a long way to converting visitors to sales. Thousands of people actively search for these specific websites in Google each month. But could page speed be negatively affecting their sales? We think so for the worst performers. Customers expect fast, slick and easy experiences. We've all experienced the pain of grappling with a website that won't do what we want it to do fast enough, so it's likely, we think, that some of the worst performers here could be dropping online sales as the result of poor speed performance.

Methodology

There's no single perfect way to measure page speed. So here's what we did to get a reasonably accurate picture:

• For each retailer, we identifed the homepage URL, three random category URLs and three random product URLs to give us a wider view of how different types of important pages on their websites perform
• We ran each URL through GTMetrix.com, using Google Chrome desktop as the browser, London as the location and an unthrottled connection. In other words, we think we've been quite kind! We've simulated what a user on desktop in London on a fast connection should experience
• We ran each URL through GTmetrix 3 times and, using the overall Page Speed Score (marked out of 100) recorded the average of 3 scores in the spreadsheet you can access below. 
• We then took an average of the scores from the 7 URLs tested across each website to give us a final overall average page speed score based on GTMetrix score.
• All of our page speed tests took place between 2nd and 4th December all between 10am and 2pm

You can access the data here.

How Does Your Page Speed Compare?

Want to test your own? Head on over to gtmetrix.com and set up a free account. You can run tests without an account but if you want to adapt your settings to simulate the results of users in the UK (rather than the default setting of Vancouver) then you'll need to sign up.

You'll then be able to switch settings as so:

The important thing to remember here to test multiple types of page. Just testing your homepage doesn't give you anywhere near a complete picture. Test a few category URLs and some product pages too.

You'll get a report that looks something like this:

Or if things aren't going so well, maybe it looks more like some of the retail websites we tested:

There's advice on GTmetrix about the specific areas of improvement. Many of these should be handled by a good platform but there's loads of advice here if that's not the case.