Building a great experience for both desktop and mobile presents an interesting problem. Mobile shoppers tend to have shorter attention spans, and thus need a faster experience relative to desktop shoppers. Yet building a fast site is more challenging on mobile, given the wide variation in network connection, processing power, and screen size. Historically, the same website viewed on both devices was typically faster on a desktop browser.

So when Retail Systems Research (RSR) released its report, “eCommerce Performance: What Works, What Doesn’t, and What’s Next?”, we were surprised by some of their findings. Specifically, the report found that eCommerce mobile websites are consistently faster than desktop sites. We dug into the numbers, and found that 83% of the sites surveyed demonstrated faster mobile load times than their desktop compatriots.

What else did the study reveal about performance on mobile and desktop devices?

Mobile is much faster: I just summarized this above, but let’s reveal the real numbers. When the eCommerce sites were measured on desktop browsers, they demonstrated an average “start render” time of 5.3 seconds and “doc complete” of 16.6 seconds. In contrast, mobile sites came in at 3.3s and 9.5s respectively – at least 35% faster! Not something we expected, but a great trend as eCommerce sites are recognizing the unique behavior of these shoppers and designing mobile sites to load faster.

Faster site = lower bounce rate: Naming one device faster requires that we address the “so what?” question. If a faster site doesn’t lead to better business results, this comparison doesn’t matter. The study revealed that on both mobile and desktop devices, sites with faster load times correlated to lower bounce rates. Meaning the faster the site, the less likely shoppers will hit the back button and leave. And lower bounce rates mean that shoppers are actively engaging on the site and, hopefully, buying products.

Which pages were slowest? These findings were also somewhat surprising. The study analyzed the homepage, a category page, and a product detail page of each site. We had expected the home page to be considerably faster that all other pages, since it’s the most common entry page and the focus of most optimization efforts. But the study found that all pages took about the same amount of time to load on each device. On desktop, the average home page loaded fastest (15.6s), but only fractionally faster than the slowest page (17.9s). And on mobile, the homepage was actually the slowest! Granted, on mobile the three different pages were only separated by a few hundred milliseconds. But it is interesting to see that mobile eCommerce teams have determined that even the rich product detail pages have to load as fast as every other page, or else you risk losing the shopper.

Desktop winners: The five fastest desktop sites were Petco, DSW, MidwayUSA, Advanced Auto Parts, and 1-800 Contacts. A telling characteristic of these sites is that 4 of them recorded the lowest percentage of time spent loading 3rd party tags. The relationship between speed and managing third parties is something we’ve covered extensively in previous posts, and it played out in this data. And the fastest page loaded in the entire study? The LuLuLemon product detail pages (<1s). Unfortunately, they didn’t make our winners list because their home and category pages didn’t meet the same standards.

Mobile winners: The five fastest mobile sites were Sephora, Shoebuy, 1-800 Contacts (repeat), Blue Nile, and DSW (repeat), all loading in under 4.3s. Like the winners in desktop, these sites required the lowest % of time to load third party tags (seeing a theme here?). The fastest page loaded on mobile devices blogs to Sephora with their product detail pages (<1s). Which is a great achievement given the rich experience on these pages where Sephora displays ratings, reviews, recommendations and large images.

This data only scratches the surface of the learnings available from the RSR study. We learned that the best eCommerce websites place a special emphasis on optimizing their mobile sites and managing 3rd party tags. We will be diving deeper into this report in the coming months, and uncovering new insights that we can apply to the upcoming Holiday 2018 season. In the meantime, download the RSR report to read their analysis and see how your site compares to your eCommerce peers.