US online shopping rose 15 percent from November 1 to December 9 compared to the same period last year, according to industry tracker comScore.
Spending reached $24.6 billion in the five-and-a-half weeks, compared to $21.4 billion in the same period of 2010, it said.
The rise in sales was boosted by the record "Cyber Monday" spending at the end of November of some $1.25 billion in a single day, with retailers attracting online buyers with promotions.
Sales at US e-commerce sites topped last year's Cyber Monday figures by 22 percent, the industry tracker reported.
Cyber Monday was launched in 2005 by a US national retail association to bring online shopping into the mainstream.