While 75% of the top 100 retail websites employ a Content Delivery Network (CDN), the median home page takes a full second longer to become interactive than the median page that does not use a CDN, according to Radware's latest quarterly study titled State of the Union: Ecommerce Page Speed & Web Performance, Spring 2014.
CDNs help bring resources closer to users by caching static page resources in distributed servers across a region or worldwide. In theory, this web performance solution reduces the amount of time it takes a host server to receive, process and deliver on a request for a page resource (images, CSS files, etc.).
Radware’s latest research shows that the median time to interact (TTI) for CDN enabled sites was 5.7 seconds compared to the median TTI of 4.7 for non-CDN websites.
“This finding should not be interpreted as a criticism of content delivery networks,” says Kent Alstad, VP of acceleration for Radware. “Instead, it should create awareness that CDNs address just one aspect of the performance problem. Web pages today are bigger and more complicated than ever, and CDNs can only partially mitigate this growth and complexity. Site owners need to be aware that there are performance issues caused by the pages themselves, and these performance issues require additional solutions.”
“While a one-second delay in interactivity does not seem significant, it can actually produce a significant negative impact on key performance indicators,” continues Alstad. “Our previous studies have shown that a one-second delay has increased bounce rates by 8.3%, decreased page views by 9.3% and even showed a 2.1% decrease in cart size, all of which can be detrimental to an eRetailer.”
Key findings from Radware’s report also include:
- The median web page has slowed down by 47% since 2012: The median top 500 ecommerce home page takes 10 seconds to load. In spring 2012, the median page loaded in 6.8 seconds. This represents a 47% slowdown in just two years. Page size is partly to blame: the median page contains 99 resources and is 1510 KB in size.
- The median page takes 5.4 seconds to become interactive: “Time to interact” (TTI) refers to how long it takes for a page’s primary content to load and become usable. For the median ecommerce page, visitors must wait 5.4 seconds for the page’s primary content to render and become usable. The majority of online shoppers will abandon a page after waiting 3 seconds for it to load.
- The top 100 sites are slower than the top 500: Higher profile sites did not fare better than their lesser-known counterparts. Among the top 100 ecommerce sites, the median load time is 10.7 seconds – 7% slower than the median load time for the top 500 sites.
- Most sites fail to leverage best practices for optimizing images: Despite the fact that images represent one of the single greatest performance challenges (and opportunities), 34% of pages failed to properly implement image compression, and 76% failed to take advantage of progressive image rendering. Each of these techniques has been proven to deliver faster real and perceived performance.
Radware’s quarterly “State of the Union” report measures and tracks the performance and page composition of the top 500 US retail websites (as ranked by analytics firm Alexa.com) with the purpose of gaining ongoing visibility into the real-world performance of leading eCommerce sites. The study also aims to learn how these sites perform for visitors using the Internet under normal browsing conditions and provides strategies and best practices to enable site owners to enhance site performance.
“We continue to see that increased page size contributes to performance issues, regardless of whether an eRetailer is using a CDN or not,” says Tammy Everts, web performance evangelist for Radware. “Many sites are not taking advantage of best practices, such as image optimization or deferring non-essential scripts after a page has completed. These fixes can be easily implemented in order to improve load times – and more importantly, the user experience – for online shoppers.”
Methodology
The tests in this study were conducted using an online tool called WebPagetest – an open-source project primarily developed and supported by Google – which simulates page load times from a real user’s perspective using real browsers. Radware tested the home page of every site in the Alexa Retail 500 nine consecutive times. The system automatically clears the cache between tests. The median test result for each home page was recorded and used in our calculations.
The tests were conducted on March 24, 2014, via the WebPagetest.org server in Dulles, VA, using Chrome 33 on a DSL connection.
In very few cases, WebPagetest rendered a blank page or an error in which none of the page rendered. These instances were represented as null in the test appendix. Also, in very few cases, WebPagetest.org rendered a page in more than 60 seconds (the default timeout for webpagetest.org). In these cases, 60 seconds was used for the result instead of null.
To identify the time to interact (TTI) for each page, we generated a timed filmstrip view of the median page load for each site in the Alexa Retail 100. Time to interact is defined as the moment that the featured page content and primary call-to-action button or menu was rendered in the frame.
