A recent audit of 500 leading mobile retail sites by Pure Oxygen Labs shows a significant jump in the number of sites using responsive design, surpassing the prevalence of dynamic serving – which many agree provides the better mobile experience.

The majority of mobile sites are still mdot, with migration away from this method of site design proceeding more slowly than expected. A key finding is that the number of retailers using responsive Web design jumped 109 percent in the past year, reaching 20 percent of the retailers on Internet Retailer’s Mobile 500.

“What might be most surprising to people is that the migration away from mdot sites isn’t happening faster given the buzz around the other methods,” said Scott Allan, head of marketing at Pure Oxygen Labs. “This could reflect the level of investment already made in these sites.

“Also tempering the pace could be the fact that when implemented correctly, mdot sites can be fast and score high points with Google and other search engines for being ‘mobile friendly,’” he said. “So for some retailers it might be a case of ‘if it works don’t fix it.’”

Time for change
Retailers may have felt an urgency to undertake site redesigns this year in expectation of Google’s algorithm change in the spring. Google provided advance notice to expect the new algorithm, which has updated search rankings based on how mobile friendly a site is. Not wanting to have their rankings take a hit, some retailers opted to redesign their sites to be mobile friendly.

This could explain why only 5 percent of sites have no mobile presence, down significantly from 14 percent in 2014.

However, with the number of mdot sites dropping from 59 percent in 2014 to 54 percent this year, this suggests many retailers are proceeding cautiously before investing in a site redesign.

For those that are making an investment, responsive design is the big winner.

Dynamic serving saw only a modest increase in use in the past year, reaching 18 percent, up from 15 percent last year.

Mdot vs. single URL
Mdot sites are burdensome to maintain. However, they can be fast and score high points with Google in search rankings.

The slow migration away from mdot sites suggests that retailers may be incorporating elements of responsiveness into their sites to adapt to small screens as a way to get more out of their investment before migrating to a new strategy.

Still, mdot sites are losing grounds to single URL strategies such as responsive design and dynamic serving as retailers prepare for the upcoming holiday season, when mobile commerce and mobile shopping are expected to grow again. Other mobile-driven trends such as cross-device advertising, app indexation, deep linking and Google buy buttons are also spurring retailers to take a close look at their mobile strategy.

Both responsive design and dynamic serving are based on a single URL, which can make it easier for retailers as they need to develop and maintain only the one site to reach consumers across platforms.

Customer experience
However, there are some important differences between the two approaches.

Responsive design automatically adjusts to the display size of a user’s devices, but this can potentially make for high page-load times, as all of the code is to delivered to a device.

Dynamic serving enables retailers to customize the user experience using different HTML and CSS on the same URL. This optimized layout approach offers fast-loading pages which logically leads to happier customers and higher conversion rates. However, dynamic serving takes more coordination among developers and more effort in customizing code to serve up to different user agents.

The fact that retailers are embracing responsive design could mean they are overcoming the load-time hurdle as they optimize content.

On the other hand, it could also mean that retailers are choosing simple implementation and maintenance over the more technical resources required for implementing and maintaining dynamic serving.

“From a mobile consumer experience standpoint the best strategy is by far is dynamic serving,” Mr. Allan said. “The reason is that different HTML and CSS can be served on the same URL to different devices or user agents.

“This allows the retailer to fully embrace mobile by customizing the experience for different devices while avoiding the speed issues sometimes presented by responsive design,” he said. ”The trade-off is that dynamic serving is more technically complex to coordinate and implement and it requires more resources to do that customization by device.

“In making these decisions, online retailers are often walking a fine line between building a great user experience and the efficient allocation of resources.”

Final Take
Chantal Tode is senior editor on Mobile Commerce Daily, New York