November 6, 2013, 5:26 PM

Mobile performance index exclusive to Internet Retailer adds more data

Keynote now is also reporting m-commerce site page size and elements count.

Lead Photo

The e-retailer's m-commerce site home page loaded in a swift 3.23 seconds, Keynote reports.

In a move designed to give retailers an even deeper understanding of mobile commerce web site performance, mobile and web performance management firm Keynote and Internet Retailer are expanding the weekly Keynote Mobile Commerce Performance Index. Previously, the index, which measures the performance of the m-commerce site home pages of 30 representative merchants, reported the load time, success rate (also known as site availability) and index score (the weighted and combined load time and success rate). Now the index will also include the size of a page in kilobytes and the number of elements on a page.

Page size is the total weight in kilobytes of all the elements loaded to create a page. The lighter the page, the quicker the load time. Large images or libraries of scripts are common contributors to heavy, slow pages, Keynote says. The element count represents the number of individual components making up a page. Elements include HTML pages, images, style sheets and scripts.

Modern web browsers, including those on smartphones, attempt to load web page elements in parallel, or simultaneously, rather than one element at a time, explains Joe Flake, mobile and web performance expert at Keynote. However, the ubiquitous page-loading protocol, hypertext transfer protocol, or HTTP, still operates using the “ask-receive-ask-receive” method, loading elements one at a time, Flake says. This slows down page load times, and it’s up to retailers to design pages in ways that work around the HTTP limitation and work with modern mobile web browsers to load page elements in parallel, he says.

“Today’s browsers are smarter, and will most likely read ahead, and see that there are additional elements to be requested, and issue a ‘get’ of Photo2—and maybe even of Photo3 and Photo4—before the response returns for the initial get of Photo1,” Flake explains. “However, JavaScript elements can block parallel loading of other elements, so retailers should put JavaScript elements at the bottom of the HTML document rather than at the top. Similarly, sometimes we see slower page loads from a misbehaving third-party server call—such as for social media or advertising or analytics—that blocks the loading of other page elements. Retailers should move these calls to after the visible parts of a page, so if they do block or take extra time, the mobile shopper will not be aware of the extra time those elements are taking to load.”

The retailer at the top of the Keynote index for the week ending Nov. 3, LLC, is a great example of effective page size and elements count, Flake says. The e-retailer’s m-commerce site home page is a tiny 60 kilobytes and contains just seven page elements.

“ is even more efficient with their seven elements, using the data URI scheme to encode four of them into the base HTML page, effectively making a download of just three individual elements,” he observes. Data URI is a scheme of encoding data within a web page that make up page elements, such as images or CSS, a mark-up language used to define pages and denote where elements appear on a page. With multiple elements encoded within a page, no extra HTTP server request is made to fetch each of the embedded elements. URI stands for universal resource identifier, a string of characters used to identify a web resource, such as an image.

Element counts on the Keynote index range from seven to 100, with sites in the top half of the index typically containing an average of 25 elements or less. Page size ranges all the way up to over 850 kilobytes, with the top five-performing mobile sites weighing in at under 100 kilobytes. “Companies striving to be top mobile performers should aim to be in the range of these numbers, 25 elements or fewer and 100 kilobytes or less,” Flake says. topped the mobile commerce performance index with a load time of 3.23 seconds and a success rate of 99.35%. Its mobile home page contains seven elements and weighs 60 kilobytes. Sears Holdings Corp. came in second with a load time of 4.01 seconds and a success rate of 99.45%; its mobile home page contains seven elements and weighs 93 kilobytes. J.C. Penney Co. Inc. came in third with a load time of 5.46 seconds and a success rate of 99.78%; its mobile home page contains 16 elements and weighs 152 kilobytes. Shopping came in fourth with a load time of 3.97 seconds and a success rate of 99.34%; its mobile home page contains 10 elements and weighs 60 kilobytes. And the averages for all 30 retailers on the index are: load time, 8.30 seconds; success rate, 98.99%; element count, 26; and page size, 302 kilobytes.

Click here then click on Keynote Mobile Commerce Performance Index Part 1 and Part 2 to view complete results for all 30 retailers on the index.

Keynote measures 30 representative m-commerce sites exclusively for Internet Retailer. The sites include merchants in multiple categories and channels, and of multiple sizes, ranging from such giants as Inc. to mid-sized retailers like LLC. Keynote tests the sites in the index every hour Monday through Sunday from 8:00 a.m. through midnight Eastern time, emulating two different smartphones on two different wireless networks: Apple Inc.’s iPhone 5 on AT&T and the Samsung Galaxy SIII on T-Mobile, both using 4G networks. Keynote runs the tests in New York and San Francisco.

Keynote combines a site’s load time and success rate, equally weighted, into a single score. Given that both performance and availability are important, the score reflects the overall quality of the home page; a higher score indicates better performance. Scores also reflect how close sites are to each other in overall quality. The index average score is the midpoint among all the sites’ scores. To consistently rank high on the Keynote index, sites must hit availability targets of 99.5% or better and be faster than 10 seconds to load on average. Top-performing sites load in under five seconds.

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