Demandware says 30 of its clients booked more than $100 million in online sales in 2015, up from 22 a year earlier.
A comScore report shows high growth for sales of iPads and other computer gear.
Online shoppers spent $30.8 billion this holiday season, up 12.8% from $27.3 billion last year, comScore reports.
The web measurement firm defines the holiday season as running from Nov. 1 through Dec. 26.
For the week ending Dec. 26, online shoppers spent $2.45 billion, up 16.6% from $2.10 billion for the corresponding period last year.
"Online holiday spending has remained strong through Christmas and we've already seen the season totals easily surpass the levels of the past few years to set a new record for spending at almost $31 billion," says comScore chairman Gian Fulgoni. "For at least this holiday season, the American consumer has been able to shrug off the continuing economic challenges of high unemployment rates and depressed housing prices and spend at a rate that has been slightly stronger than we had expected. After the past few years' struggles, it is gratifying to see e-commerce return to a state that can only be described as a very merry holiday shopping season.”
For product categories, computer hardware had the highest rate of sales growth, up 23% from last year, thanks in part to sales of e-reading devices and Apple Inc.’s iPad.
Books and magazines were the second fastest growing category, 22%, followed by consumer electronics, 21%, computer software not including games, 20%, toys, 16%, and jewelry and watches, 11%.