It wasn't all bad for retailers this holiday season.
Days after the National Retail Federation reported that holiday sales growth fell short of its forecast, data from Adobe Digital Index found that online sales hit a record $83 billion in November and December, easily beating the firm's expectations.
According to Adobe, online sales rose 12.7 percent during the final two months of the year, surpassing its forecast for 11 percent growth. It also marks a slight acceleration from 2014, when Adobe said holiday sales increased by 12 percent.
Results were lifted by a late-in-the season boost from mobile shoppers, as a spike in smartphone traffic led to an increase in sales. What's more, the option to pick up gifts in the store made consumers more comfortable placing last-minute online orders.
"In years past, at least, as you get closer to Christmas people quit shopping online because they're afraid they're not going to get their items in time," said Tyler White, senior manager for Adobe Digital Index Data Science. "That was not true this year."
According to Adobe, which compiles its data from 1 trillion visits to more than 4,500 retail websites, digital sales spiked 56 percent year over year in the week prior to Christmas, to $920 million. That compares with an average week's growth of 40 percent, White said.
While White called those gains "impressive," sales for that week were still well short of the season's biggest days. According to Adobe's data, Cyber Monday revenue hit an all-time high for a single day, at $3.07 billion. It was followed by Black Friday, which generated $2.74 billion, and the second Monday of December, known as "Green Monday," which rung up $1.89 billion in sales.
According to Adobe, online retailers posted 31 billion-dollar days during the holidays, all of which were between Nov. 22 and Dec. 22. That compares with 25 such days last season. Overall, holiday sales accounted for 28 percent of annual online sales, Adobe said.
Fueling the growth in online revenues was a larger-than-expected shift to mobile, which White attributed to a larger adoption of smartphones.
Whereas tablet traffic declined from a 14 percent share in 2014 to 11 percent in 2015, smartphone's share grew from 30 percent to 39 percent. Desktop traffic declined from 56 percent to 50 percent share.
In terms of sales, phone revenue grew 52 percent to $14 billion, while those from tablets fell 3 percent to $9 billion. On desktop, revenue rose 4 percent to $60 billion.
Though desktop remained the largest driver of visits and sales — at 50 percent and 73 percent, respectively — there were six days when traffic from smartphones surpassed that from desktop. Prior to this holiday season, that had never happened, according to Adobe.
White said the days that skewed toward smartphones tended to be on the weekends and as Christmas drew closer, when shoppers did not necessarily have access to desktop computers, White said.
On Christmas, when traffic from smartphones peaked at 49 percent of digital visits, it nearly surpassed traffic from desktop and tablet devices combined.
"That's a big deal," White said.
Adobe's insights follow preliminary results from comScore, which found that a boom in mobile sales will likely not be enough to make up for softer-than-expected trends on desktop computers.
According to comScore, it now expects overall online sales to have increased 13 percent this holiday season, compared with its original forecast for 14 percent growth.
Not surprisingly, Amazon is expected to be the big winner from the season's online surge. A recent note from Cowen and Co., citing ComScore data, said the total number of visits to Amazon this holiday was equal to the next four retailers combined. Those four retailers were eBay, Wal-Mart, Target and Macy's.
"Amazon is kicking the pants off of everybody, and I think that's the future," Marcum's Ron Friedman said Friday.
Overall, the National Retail Federation reported that retail sales excluding automobiles, gas stations and restaurants increased 3 percent in November and December, to $626.1 billion. That compares with its forecast for a 3.7 percent increase, and last year's 4.1 percent growth.