Walmart (NYSE:WMT) has added another e-commerce trophy to its growing list of accolades: The big-box retailer has surpassed online pioneer eBay (NASDAQ:EBAY) for a share of e-commerce sales in the U.S. for the first time in May 2020, according to eMarketer.

eBay has long trailed digital sales leader (NASDAQ:AMZN), which accounts for 38% of online shopping in the country. Walmart has now moved into the No. 2 spot with 5.8% of digital retail, while eBay slipped into third with 4.5%.

A smiling couple making an ecommerce purchase using a laptop to enter credit card information.

Image source: Getty Images.

During Walmart's first quarter, which ended May 1, the company reported e-commerce sales that jumped 74% year over year, with strong contributions from its grocery pickup and delivery services,, and its marketplace. During eBay's first quarter, which ended March 31, its marketplace revenue -- which excludes its classifieds business -- fell 1% year over year. This illustrates that Walmart was gaining share as eBay was losing it, even in a period that was a strong one for digital sales. 

E-commerce sales in the U.S. increased nearly 15% year over year during the first quarter of 2020 and accounted for 12% of total retail, according to the U.S. Department of Commerce. 

eMarketer estimates that e-commerce sales will increase 18% year over year in 2020, eclipsing its earlier forecast of 13% growth. At the same time, overall retail sales are expected to decline 10.5%.

There has been a widely reported shift in consumer buying behavior as the result of the COVID-19 coronavirus pandemic. With widespread stay-at-home orders and employees shifting to remote work, many customers choose the ease and convenience of e-commerce, foregoing trips to brick-and-mortar retail stores for fear of contracting the virus. Unfortunately, eBay was unable to capitalize on the shift.