The figures by IBM Benchmark were released at noon, Eastern time. They suggest that nearly a third of all online shopping traffic was done by way of mobile devices like smartphones and tablets.
Cyber Monday, the Monday after Thanksgiving, is supposed to be the busiest day of the year for online shopping.
Retailers failed to boost spending during the four-day holiday weekend. They had offered big discounts in early November, and several retailers opened stores on Thanksgiving Day. But the National Retail Federation estimates that spending fell for the first time ever -- down 2.8 percent -- during the four days that ended yesterday.
The NRF's online arm says more than 4 out of 5 retailers were planning to offer deals specifically for Cyber Monday.