With mobile commerce growing at a rate more than double the growth of total e-commerce, the future of e-commerce appears to be a mobile one.

In the U.S., which invented e-retailing based on desktop devices, two-thirds of the time spent by consumers shopping online is now spent on smartphones and tablets, while 38% of 2016 online retail sales are projected to come via mobile devices, according to Forrester Research Inc., up from less than 10% just a few years ago.

This shift to mobile-based e-commerce from desktop is lifting the prospects of some leading web merchants and depressing them for others. This competitive challenge to the e-commerce elite can be seen by comparing the world’s 25 largest e-commerce competitors, as ranked by Internet Retailer’s recently released Global 1000 Database, to the world’s 25 largest mobile commerce competitors, which are ranked in IR’s 2017 Mobile 500, published earlier this month.

These rankings show that some of the world’s largest e-commerce players are losing ground in the faster-growing mobile commerce field. In fact, 10 of the top 25 global e-commerce companies do not appear among the 25 largest mobile commerce operators, having been replaced on that list by rivals that do not rank among the 25 largest online retailers in the Global 1000.

Worldwide e-commerce leaders such as Dell (No. 6 in the Global 1000), Home Depot Inc. (No. 16), Costco Wholesale Corp. (No. 17), W.W. Grainger Inc. (No. 19), Best Buy Co. Inc. (No. 20) and CDW (No. 21) are nowhere to be found on the list of the 25 largest mobile commerce operators. Dell, for instance, ranks No. 87 in mobile commerce, while Home Depot is No. 34, Costco No. 52, Grainger No. 139, Best Buy No. 37 and CDW Corp. is not ranked at all in the 2017 Mobile 500.

Conversely, 10 companies that appear among the 25 largest mobile commerce competitors are not among the 25 largest companies based on total e-commerce volume. They include ninth-ranked Jumei.com, John Lewis PLC (No. 10), Etsy Inc. (No. 19) and Newegg Inc. (No. 25).

A total of 15 e-retailers appear on both top 25 lists. Of those, seven competitors rank higher in mobile commerce than overall e-commerce, including Gome Electrical Appliances Holding Ltd., Suning Appliance Co. Ltd., Vipshop Holdings Ltd., Google Play, Home Retail Group (Argos), QVC Group and Zalando SE. Five of the top 25 leaders in the Global 1000 have lower rankings in the top 25 mobile competitors, including Xiaomi, Wal-Mart Stores Inc., Otto Group, Macy’s Inc. and Staples Inc. Meanwhile, three companies rank one, two and three on both lists (Amazon.com Inc., JD.com Inc. and Apple Inc., respectively).

These comparative rankings affect the overall e-commerce growth of the companies involved because the 500 largest mobile commerce retailers worldwide are growing their mobile sales 53% annually, while the 1,000 largest overall global e-commerce competitors last year grew total web sales by 23%. So it should be no surprise that the 10 e-retailers that are ranked among the top 25 mobile commerce operators but were excluded from the top 25 in total e-commerce, grew at a faster rate than the 10 e-retailers ranked among the top 25 in global e-commerce but not ranked among the top 25 global mobile e-retailers. What’s surprising is that the difference between the growth rates of those two groups is so great. The 10 e-retailers ranked in the mobile commerce top 25 but not included among the 25 top global e-commerce companies grew their total web sales last year by an average 25%, while web merchants ranked in the top 25 of global e-commerce but excluded from the top 25 in mobile commerce grew their average web sales by just 7.5%.

There are some external factors that affect these comparisons. Principal among them is the home market of the e-retailers being compared. Seven of the top 25 mobile commerce players are based in China, where online shopping is overwhelmingly performed on mobile devices.  Another factor may well be the client base that the retailer primarily serves. For instance, Dell, No. 6 among all e-commerce operators but No. 87 among mobile commerce competitors, caters heavily to commercial clients, who place orders primarily on desktop computers.

Still, the compelling theme of these comparisons is stark: The major global web merchants aggressively targeting a mobile commerce market are growing faster than their peers who are falling behind the mobile commerce adoption curve. Anyone looking for the future leaders of global e-commerce is well-advised to look at the top mobile commerce players, not today’s top e-commerce competitors.