Retailer Gilt Groupe Inc. conducts short-term flash sales, offering a limited selection of luxury goods for a brief time, usually a few days or until an item sells out. That means many of its customers visit the retailer’s mobile site on the go so as not to miss a stellar deal. However, some of those shoppers likely encountered a sluggish mobile site last week, according to data compiled for this week’s AppDynamics/Mobile Strategies 360 Performance Index. The index ranks 30 company mobile sites based on their performance.
“This week’s data shows that Gilt Groupe had the biggest change, particularly in 3G, but also in 4G, primarily due to an increased (home) page weight,” says Peter Kacandes, senior product marketing manager, mobile, web and synthetics, at AppDynamics. For 3G networks, the retailer’s home page weight increased from 2.75 megabytes for the week ending Aug. 9 to 3.36 megabytes for the week ending Aug. 16, Kacandes says, a 22% increase.
The increased home page weight led to an increase in 3G visually complete time, or the time it takes, in seconds, until the web browser has completed drawing the visual elements of a page. Visually complete time rose to 15 seconds for the week ending Aug. 16 from 9.3 seconds a week earlier. That increased the retailer’s mobile Speed Score from 5 seconds last week to 7.1 seconds this week. This caused a drop in the ranking from 4th place to 9th place for the week ending Aug. 16.
“There was very clearly a change in the site with an accompanying increase in page weight on Aug. 11 around noon, which continued throughout most of the week until there was another jump at 9 a.m. on Aug.16 before returning to earlier levels at 9 a.m. on Aug. 17,” Kacandes says.
Due to the higher speed of 4G networks, the changes weren’t as dramatic on 4G, but the increased page weight week over week (1.73 megabytes to 2.32 megabytes) still increased visually complete time from 5.1 to 5.5 seconds. That jacked up its 4G Speed Score from 2.7 to 3.5 seconds and dropped Gilt to No. 7 for the week ending Aug. 16 compared to No. 5 a week earlier.
Gilt didn’t immediately respond to a request to comment on its mobile site performance.
The exclusive AppDynamics/Mobile Strategies 360 Index tracks key mobile site metrics across a range of sites to calculate a weekly average Speed Score on both 3G and 4G mobile carrier networks. The index represents a snapshot of mobile site performance across industries, including retailers such as HSN.com, insurance companies such as NorthwesternMutual.com and restaurants such as McDonalds.com.
AppDynamics each week measures performance metrics of both 3G and 4G networks for each of the 30 sites in the index to determine each site’s Speed Score.
They include:
First render: The time, (in seconds) it takes until the web browser starts drawing the visual elements of a page.
Visually complete: The time (in seconds) it takes until the web browser has completed drawing the visual elements of a page.
Number of elements loaded: The number of resources loaded by a page.
Complete load: The size of the home page when all data is loaded (in megabytes).
Using these metrics, the index calculates the Speed Score. The Speed Score is a ratio that rewards businesses for displaying more visual content earlier rather than later. The earlier a mobile site looks complete to a consumer, the better the mobile experience for the visitor, even if a few remaining elements are displayed later. A site with a higher ratio of content displayed earlier will have a better Speed Score than a site with the same visually complete time but a longer first render time.
For example, site A may have a visually complete time of three seconds, loading 90% of its content in the first second and the remaining 10% in seconds two and three. Site B may have the same three-second visually complete time, but present zero content in the first two seconds and 100% in the third second. The sites have identical visually complete times, but Site A will be perceived as much faster, and will earn a better Speed Score as a result.
The index displays the average across the 30 mobile sites for each metric as well as the average Speed Score on both 3G and 4G networks.
For the week ending Aug. 16, the average Speed Score for 3G was 9.3 seconds, compared with 9.2 seconds a week earlier. The average first render was 6.2 seconds, the same as a week earlier.
Visually complete average was 15.5 seconds compared to 14.9 seconds a week earlier. Average number of elements loaded was 87.1 compared to 87.8 a week earlier. Average home page weight was 2.5 megabytes, compared with 2.4 megabytes a week earlier.
On 4G, the average Speed Score was 5.2 seconds, the same as a week earlier. The average first render was 3.6 seconds the same as a week earlier.
Visually complete average time was 8.4 seconds compared to 8.5 seconds the previous week. Average number of elements loaded was 83.7 versus 85.2 a week earlier. And average weight was 1.5 megabytes compared with 1.4 megabytes a week earlier.
The index is accompanied by a chart on MobileStrategies360.com that is refreshed weekly to illustrate how each mobile site performs as well as index averages. Click here to access the performance chart for the week ending Aug. 16, 2015.
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