A survey showed that US online shoppers clicked their way to a new record for "Cyber Monday," boosting sales by 30.3 percent for the traditional start for Internet holiday shopping.
IBM said its cloud-based digital analytics platform showed Monday was "the biggest spending day ever" for US online consumers.
"Cyber Monday was not only the pinnacle of the Thanksgiving shopping weekend but when the cash register closed it officially became the biggest online shopping day ever," said Jay Henderson of IBM Smarter Commerce.
"Retailers that adopted a smarter marketing approach to commerce were able to adjust to the shifting shopping habits of their customers, whether in-store, online or via their mobile device of choice, and fully benefit from this day and the entire holiday weekend."
Around 10 percent of consumers made purchases on a mobile device, according to IBM, with the iPhone the most popular one.
IBM offered no specific figure for sales but the research firm comScore has predicted retailers would take in $1.5 billion for the day, a jump of 20 percent.
The hot Monday sales came after surveys showed heavy online spending for "Black Friday," the day after the US Thanksgiving holiday.
Online shoppers spent a record of $1.042 billion on Friday, surpassing last year's Black Friday haul by 26 percent, according to comScore.
A total of 57.3 million Americans visited online retail sites on Black Friday, representing an increase of 18 percent versus a year ago, the firm said.