Shoppers weren't afraid to pull out their smartphones to shop on Thanksgiving, to the tune of $1 billion.

Sales online Thanksgiving Day totaled $3.7 billion, up 28 percent from a year ago, Adobe Analytics said in a report Friday. That makes Thursday the fastest-growing day for e-commerce sales in history, added the firm, which tracks transactions from 80 of the top 100 internet retailers. Thursday was also the first day in 2018 to see $1 billion in sales from smartphones, according to Adobe, with shoppers spending 8 percent more online on Thursday compared with a year ago.

With more shoppers browsing sites such as Amazon for deals during the holidays, the move is seen as starting to steal some of Black Friday's thunder, when typically throngs of shoppers head to malls across the U.S.

"Overall, Black Friday doesn't have the sense of urgency as in the past and feels more like a busy regular weekend day in many of the stores," Telsey Advisory Group analyst Dana Telsey said in a research note. Many promotions have been available "for the past couple of weeks," she added, making it less of a necessity for shoppers to flock to stores the day after Turkey Day to score a deal.

Real estate services provider JLL said it polled 60 U.S. mall managers about store traffic patterns on Black Friday. On the West Coast, none of the mall operators said traffic was better than last year. Roughly 86 percent said traffic was the same as last year, and about 14 percent said it was less. On the East Coast, 32 percent of managers said traffic was up at malls, while 46 percent said it was the same compared with last year, and 23 percent said it was less.

Online spending is, meanwhile, expected to hit more than $6.4 billion on Black Friday, either matching or exceeding Cyber Monday of 2017, Adobe said. As of 10 a.m. ET Friday, $643 million had already been spent online.

Kohl's said it had a record day for digital sales on Thanksgiving, with 80 percent of online traffic coming from mobile devices. Walmart and Target also called out strong traffic online, with a lot of customers this year opting to buy online and pick up in store. Shoppers nearly doubled their click-and-collect orders from Wednesday to Thursday this week, Adobe said.

"Retailers understand that shopping and buying on smartphones is now the norm for consumers, and as a result are delivering better experiences and optimization on mobile devices," said Taylor Schreiner, director of Adobe Digital Insights.

The National Retail Federation is predicting holiday sales gains — in stores and online — will be better than a five-year average of 3.9 percent. It expects a bump ranging from 4.3 percent to 4.8 percent.