March 7, 2013, 4:19 PM

An object lesson in mobile commerce site performance

Minimizing the number of page objects is key to fast page load times, Keynote says.

Mobile commerce web site pages are built using various kinds of objects. An object could be an image, a box of text, a tracking pixel or a web analytics call, among other things.

Mobile performance is measured by success rate, also known as availability, which is the percentage of the time a site completely and successfully loads, and by load time, the amount of time in seconds it takes to load a page.

The most important factor in determining page load time is the number and type of objects being loaded within a mobile web browser, says Haroon Chohan, mobile and web performance expert at Keynote.

“When we look at page load times, we’re looking at how long it takes for the entire page to finish loading within a browser, which means every object regardless if it is visible to the end user or not,” Chohan says. “For example, there may be a number of tracking and web analytic objects that an end user would not even be aware of; however, they are still loading within the browser and are included in the overall page load time metrics that Keynote captures.”

While the consumer might not see these kinds of objects, they still can impact performance in a noticeable way. For example, an invisible JavaScript object might prevent any other object—such as images or text—from loading on the page until it has finished executing, thus impacting the shopper’s experience, Chohan says. And third-party tracking pixels which are not visible to consumers could  cause major latency issues while loading on a page; if the tracking pixel is being called before some of the other visible objects load on the page, any latency by the invisible tracking pixel would impact the shopper’s experience, Chohan explains.

For mobile web sites, it’s important to keep the number of objects loading within the browser on the home page to 10 or fewer, Chohan advises. 10 to 30 is tolerable, but more than 30 often leads to performance problems, he adds. “Keeping the number of objects loading within the browser to a minimum can greatly improve browser page load times and prevent unexpected latency issues,” he says.

The top five performers on the Keynote Mobile Commerce Performance Index for the week ending March 3 are examples of sensible management of home page object counts, Keynote says.

W.W. Grainger Inc. topped the index with an m-commerce site home page load time of 4.50 seconds and a success rate of 99.67% for an index score of 939 out of 1,000. Its home page contains nine objects. Barnes & Noble came in second with a load time of 5.44 seconds and a success rate of 99.78% for a score of 936. Its home page contains 22 objects. Office Depot Inc. came in third with a load time of 5.20 seconds and a success rate of 99.67% for a score of 923. Its home page contains 11 objects.

Amazon.com Inc. came in fourth with a load time of 6.99 seconds and a success rate of 99.78% for a score of 903. Its home page contains 15 objects. And Sears Holdings Corp. came in fifth with a load time of 5.06 seconds and a success rate of 99.45% for a score of 890. Its home page contains nine objects.

Grainger is No. 76 in the Internet Retailer Mobile 400, BarnesandNoble.com Inc. No. 31, Office Depot No. 65, Amazon.com No. 1 and Sears No. 29.

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

Keynote Systems 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 Amazon.com Inc. to midsized retailers like Toolfetch.com LLC. Keynote tests the sites in the index every hour Monday through Sunday from 8 a.m. through midnight Eastern time, emulating three different smartphones on three different wireless networks: Apple Inc.’s iPhone 4 on AT&T, the HTC Evo on Sprint and the Droid X on Verizon. The HTC Evo and the Droid X run Google Inc.’s Android operating system. 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.

Keynote is ranked No. 2 among web performance monitoring firms in Internet Retailer’s Leading Vendors to the Top 1000 E-retailers guide.

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