December 5, 2012, 2:13 PM

PetSmart puts on weight, and it shows

More kilobytes on its mobile home page translates into slower load times, Keynote says.

Lead Photo

For the week ending Dec. 2, the retailer's m-commerce site home page loaded on average in 7.85 seconds, up 24% from 6.31 seconds the previous week.

PetSmart Inc. on Nov. 29 made a variety of changes to its mobile commerce web site, changes that added heft to its mobile home page and slowed down performance, according to the Keynote Mobile Commerce Performance Index.

“When comparing its mobile site with the previous week, this week we saw PetSmart doubling its page size and increasing the number of page elements, which suggested significant changes to its mobile site,” says Venkatesh Giri, mobile performance evangelist at Keynote Systems Inc. “The changes made are all under the hood and are not a site redesign.”

For the week ending Dec. 2, PetSmart’s m-commerce site home page loaded on average in 7.85 seconds and did so completely and successfully 99.14% of the time. The weighted and combined load time and success rate earned PetSmart an index score of 775 out of 1,000. For the week ending Nov. 25, PetSmart registered a load time of 6.31 seconds and a success rate of 97.45% for a score of 700. PetSmart earned a better score this week solely on the strength of its improved success rate even as its page load time increased 24%.

Before the Nov. 29 changes, PetSmart’s m-commerce site home page served 13 page objects, such as images or boxes of text, and weighed approximately 100 kilobytes, Keynote says. PetSmart’s current home page sports 20 elements that weigh 200 kilobytes, the measurement firm says. Among the new elements is an application program interface, or API, for the newly added Google Ajax Search, which facilitates quicker loading of search results pages, Keynote says. PetSmart’s mobile home page also includes an API for Google Commerce Search, the backbone of the merchant’s site search, the firm adds.

“To load these different Google APIs, PetSmart is using Google’s autoloader, which allows you to easily import one or more APIs into a mobile site,” Giri says. “Savvy developers can use auto-loading to enhance the performance of a mobile site.”

The addition of new functionality is welcome, but the increase in page size and the number of elements means the loading of the m-commerce site is slower than the previous week, Giri says.

“PetSmart must first focus on reducing the number of elements, making fewer HTTP server requests wherever possible to improve page loading,” Giri says. An HTTP server request occurs when a mobile web browser on a smartphone requests page elements from a retailer’s server. “PetSmart serves nine images, and what caught our attention was how PetSmart is not using any image-optimization techniques to reduce the number of elements. They are serving individual site icon images instead of using Cascading Style Sheet sprites, a technique which combines multiple images into a single sprite image. Implementing this technique will reduce the number of elements and balance out the extra HTTP requests required to load Google APIs.”

Further, PetSmart uses data compression techniques on a few page objects to reduce the weight of the home page but doesn’t make use of these techniques consistently, Giri adds.

“For example, its home page is not compressed and very few of its JavaScript files are compressed,” Giri says. “If the retailer wishes to climb up the index, it needs to focus on optimizing its web site after the addition of new functionalities. Developers and designers need to ensure that adding new functionality doesn’t cause web site slow-downs or negatively impact site performance.”

PetSmart did not immediately respond to a request for comment.

For the week ending Dec. 2, Barnes & Noble and LLC tied for first place on the Keynote Mobile Commerce Performance Index. Barnes & Noble registered a load time of 5.22 seconds and a success rate of 100% for a score of 946. had a load time of 2.87 seconds and a success rate of 99.58% for a score of 946. Office Depot Inc. came in third with a load time of 3.61 seconds and a success rate of 99.68% for a score of 942.

The index average load time was 9.47 seconds, the average success rate was 99.05% and the average score was 727.

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 Inc. to midsized retailers like 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 one another in overall quality. The index average score is the midpoint among all the sites’ scores.

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